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Showing 1 - 200 of 3120 Journals sorted alphabetically
A Practical Logic of Cognitive Systems     Full-text available via subscription   (Followers: 8)
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 26, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 22, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 90, SJR: 1.109, h-index: 94)
Accounting Forum     Hybrid Journal   (Followers: 25, SJR: 0.612, h-index: 27)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 30, SJR: 2.515, h-index: 90)
Achievements in the Life Sciences     Open Access   (Followers: 4)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 5, SJR: 0.338, h-index: 19)
Acta Astronautica     Hybrid Journal   (Followers: 379, SJR: 0.726, h-index: 43)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 3)
Acta Biomaterialia     Hybrid Journal   (Followers: 26, SJR: 2.02, h-index: 104)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 1)
Acta de Investigación Psicológica     Open Access   (Followers: 2)
Acta Ecologica Sinica     Open Access   (Followers: 8, SJR: 0.172, h-index: 29)
Acta Haematologica Polonica     Free   (Followers: 1, SJR: 0.123, h-index: 8)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.604, h-index: 38)
Acta Materialia     Hybrid Journal   (Followers: 237, SJR: 3.683, h-index: 202)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.615, h-index: 21)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.442, h-index: 21)
Acta Oecologica     Hybrid Journal   (Followers: 10, SJR: 0.915, h-index: 53)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription   (Followers: 1)
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 3, SJR: 0.311, h-index: 16)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 2)
Acta Poética     Open Access   (Followers: 4)
Acta Psychologica     Hybrid Journal   (Followers: 25, SJR: 1.365, h-index: 73)
Acta Sociológica     Open Access  
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.059, h-index: 77)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 4)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 3)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 4, SJR: 0.383, h-index: 19)
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Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 5, SJR: 0.141, h-index: 3)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 4, SJR: 0.112, h-index: 2)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 5)
Acute Pain     Full-text available via subscription   (Followers: 13)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.967, h-index: 57)
Addictive Behaviors     Hybrid Journal   (Followers: 15, SJR: 1.514, h-index: 92)
Addictive Behaviors Reports     Open Access   (Followers: 7)
Additive Manufacturing     Hybrid Journal   (Followers: 7, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 22)
Advanced Cement Based Materials     Full-text available via subscription   (Followers: 3)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 139, SJR: 5.2, h-index: 222)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 11, SJR: 1.265, h-index: 53)
Advanced Powder Technology     Hybrid Journal   (Followers: 17, SJR: 0.739, h-index: 33)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.299, h-index: 15)
Advances in Agronomy     Full-text available via subscription   (Followers: 15, SJR: 2.071, h-index: 82)
Advances in Anesthesia     Full-text available via subscription   (Followers: 27, SJR: 0.169, h-index: 4)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 4)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 9, SJR: 1.054, h-index: 35)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 12, SJR: 0.801, h-index: 26)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 23, SJR: 1.286, h-index: 49)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 16, SJR: 3.31, h-index: 42)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.277, h-index: 43)
Advances in Botanical Research     Full-text available via subscription   (Followers: 3, SJR: 0.619, h-index: 48)
Advances in Cancer Research     Full-text available via subscription   (Followers: 26, SJR: 2.215, h-index: 78)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 0.9, h-index: 30)
Advances in Catalysis     Full-text available via subscription   (Followers: 6, SJR: 2.139, h-index: 42)
Advances in Cell Aging and Gerontology     Full-text available via subscription   (Followers: 4)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 13)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 26, SJR: 0.183, h-index: 23)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.665, h-index: 29)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 9, SJR: 1.268, h-index: 45)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 29, SJR: 0.938, h-index: 33)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18, SJR: 2.314, h-index: 130)
Advances in Computers     Full-text available via subscription   (Followers: 16, SJR: 0.223, h-index: 22)
Advances in Dermatology     Full-text available via subscription   (Followers: 12)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 12)
Advances in Digestive Medicine     Open Access   (Followers: 7)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 6)
Advances in Drug Research     Full-text available via subscription   (Followers: 23)
Advances in Ecological Research     Full-text available via subscription   (Followers: 47, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 27, SJR: 0.486, h-index: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 9)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 46, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 3)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 52, SJR: 0.674, h-index: 38)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Genetics     Full-text available via subscription   (Followers: 17, SJR: 2.558, h-index: 54)
Advances in Genome Biology     Full-text available via subscription   (Followers: 11)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 2.325, h-index: 20)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 22, SJR: 0.906, h-index: 24)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 0.497, h-index: 31)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 27)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 2, SJR: 0.396, h-index: 27)
Advances in Immunology     Full-text available via subscription   (Followers: 36, SJR: 4.152, h-index: 85)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 1.132, h-index: 42)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 3, SJR: 1.274, h-index: 27)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 4)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.764, h-index: 15)
Advances in Lipobiology     Full-text available via subscription   (Followers: 2)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 10)
Advances in Marine Biology     Full-text available via subscription   (Followers: 16, SJR: 1.645, h-index: 45)
Advances in Mathematics     Full-text available via subscription   (Followers: 10, SJR: 3.261, h-index: 65)
Advances in Medical Sciences     Hybrid Journal   (Followers: 6, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 5, SJR: 1.44, h-index: 51)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 23)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 10)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 9, SJR: 0.324, h-index: 8)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 4)
Advances in Oncobiology     Full-text available via subscription   (Followers: 2)
Advances in Organ Biology     Full-text available via subscription   (Followers: 2)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15, SJR: 2.885, h-index: 45)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.148, h-index: 11)
Advances in Parasitology     Full-text available via subscription   (Followers: 7, SJR: 2.37, h-index: 73)
Advances in Pediatrics     Full-text available via subscription   (Followers: 24, SJR: 0.4, h-index: 28)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 13)
Advances in Pharmacology     Full-text available via subscription   (Followers: 16, SJR: 1.718, h-index: 58)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.384, h-index: 26)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.248, h-index: 11)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 7)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 5)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20, SJR: 1.5, h-index: 62)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6, SJR: 0.478, h-index: 32)
Advances in Radiation Oncology     Open Access  
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 3, SJR: 0.1, h-index: 2)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 5)
Advances in Space Research     Full-text available via subscription   (Followers: 370, SJR: 0.606, h-index: 65)
Advances in Structural Biology     Full-text available via subscription   (Followers: 8)
Advances in Surgery     Full-text available via subscription   (Followers: 9, SJR: 0.823, h-index: 27)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 31, SJR: 1.321, h-index: 56)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 16)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 13)
Advances in Virus Research     Full-text available via subscription   (Followers: 6, SJR: 1.878, h-index: 68)
Advances in Water Resources     Hybrid Journal   (Followers: 45, SJR: 2.408, h-index: 94)
Aeolian Research     Hybrid Journal   (Followers: 5, SJR: 0.973, h-index: 22)
Aerospace Science and Technology     Hybrid Journal   (Followers: 338, SJR: 0.816, h-index: 49)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.318, h-index: 36)
African J. of Emergency Medicine     Open Access   (Followers: 6, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 9, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 432, SJR: 1.385, h-index: 72)
Agri Gene     Hybrid Journal  
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 15, SJR: 2.18, h-index: 116)
Agricultural Systems     Hybrid Journal   (Followers: 31, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 42, SJR: 1.546, h-index: 79)
Agriculture and Agricultural Science Procedia     Open Access  
Agriculture and Natural Resources     Open Access   (Followers: 3)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 56, SJR: 1.879, h-index: 120)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.434, h-index: 14)
Air Medical J.     Hybrid Journal   (Followers: 5, SJR: 0.234, h-index: 18)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.285, h-index: 3)
Alcohol     Hybrid Journal   (Followers: 11, SJR: 0.922, h-index: 66)
Alcoholism and Drug Addiction     Open Access   (Followers: 8)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 1, SJR: 0.436, h-index: 12)
Alexandria J. of Medicine     Open Access   (Followers: 1)
Algal Research     Partially Free   (Followers: 9, SJR: 2.05, h-index: 20)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.46, h-index: 29)
Allergology Intl.     Open Access   (Followers: 4, SJR: 0.776, h-index: 35)
Alpha Omegan     Full-text available via subscription   (SJR: 0.121, h-index: 9)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 9, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 49, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 4)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 5)
American Heart J.     Hybrid Journal   (Followers: 48, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 48, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 42, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 9, SJR: 1.091, h-index: 45)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 32, SJR: 8.769, h-index: 256)
American J. of Infection Control     Hybrid Journal   (Followers: 26, SJR: 1.259, h-index: 81)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 31, SJR: 2.313, h-index: 172)
American J. of Medicine     Hybrid Journal   (Followers: 45, SJR: 2.023, h-index: 189)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 208, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 61, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 6)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.249, h-index: 88)
American J. of Otolaryngology     Hybrid Journal   (Followers: 24, SJR: 0.59, h-index: 45)
American J. of Pathology     Hybrid Journal   (Followers: 27, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 26, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 36, SJR: 1.286, h-index: 125)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.653, h-index: 70)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 6)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 60, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 14)
Anales de Cirugia Vascular     Full-text available via subscription  
Anales de Pediatría     Full-text available via subscription   (Followers: 2, SJR: 0.209, h-index: 27)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription   (SJR: 0.104, h-index: 3)
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 4, SJR: 2.577, h-index: 7)
Analytica Chimica Acta     Hybrid Journal   (Followers: 36, SJR: 1.548, h-index: 152)
Analytical Biochemistry     Hybrid Journal   (Followers: 171, SJR: 0.725, h-index: 154)
Analytical Chemistry Research     Open Access   (Followers: 8, SJR: 0.18, h-index: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 12)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 1)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 22, SJR: 0.421, h-index: 40)
Angiología     Full-text available via subscription   (SJR: 0.124, h-index: 9)
Angiologia e Cirurgia Vascular     Open Access  
Animal Behaviour     Hybrid Journal   (Followers: 176, SJR: 1.907, h-index: 126)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 5, SJR: 1.151, h-index: 83)

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Journal Cover Advances in Space Research
  [SJR: 0.606]   [H-I: 65]   [370 followers]  Follow
   Full-text available via subscription Subscription journal
   ISSN (Print) 0273-1177
   Published by Elsevier Homepage  [3123 journals]
  • Preface: MHD wave phenomena in the solar interior and atmosphere
    • Authors: Viktor Fedun; A.K. Srivastava
      Pages: 593 - 594
      Abstract: Publication date: 15 January 2018
      Source:Advances in Space Research, Volume 61, Issue 2
      Author(s): Viktor Fedun, A.K. Srivastava

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.12.004
  • Kink mode m=1 in magnetic tube with discontinuous magnetic field
    • Authors: O.K. Cheremnykh; A.N. Kryshtal; A.A. Tkachenko
      Pages: 603 - 610
      Abstract: Publication date: 15 January 2018
      Source:Advances in Space Research, Volume 61, Issue 2
      Author(s): O.K. Cheremnykh, A.N. Kryshtal, A.A. Tkachenko
      In this paper, we study conditions of realization and stability of kink modes with azimuthal wave numbers m = ± 1 in cylindrical plasma flex with twisted magnetic field and homogeneous current along its axis. We assume permanent axial magnetic field both inside and outside the flex, surrounded by currentless plasma. Azimuthal magnetic field decreases inversely proportional to the distance from the boundary beyond the flex. We derived dispersion equations for stable and unstable modes in approximation of “thin” plasma flex. The analysis of equations has been provided for the case of discontinuous axial magnetic field on flex’s boundary. Conditions of propagation of wave modes have been defined. It was shown, that unstable modes can be implemented in certain interval of longitudinal wavenumbers. Results can be applied for the interpretation of solar magnetic tubes behavior, using measurements, provided by spacecrafts.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.05.026
  • Quasi-biennial oscillations in the cross-correlation of properties of
    • Authors: T.S. Kiss; N. Gyenge; R. Erdélyi
      Pages: 611 - 616
      Abstract: Publication date: 15 January 2018
      Source:Advances in Space Research, Volume 61, Issue 2
      Author(s): T.S. Kiss, N. Gyenge, R. Erdélyi
      Jets, whatever small (e.g. spicules) or large (e.g. macrospicules) their size, may play a key role in momentum and energy transport from photosphere to chromosphere and at least to the low corona. Here, we investigate the properties of abundant, large-scale dynamic jets observable in the solar atmosphere: the macrospicules (MS). These jets are observationally more distinct phenomena than their little, and perhaps more ubiquitous, cousins, the spicules. Investigation of long-term variation of the properties of macrospicules may help to a better understanding of their underlying physics of generation and role in coronal heating. Taking advantage of the high temporal and spatial resolution of the Solar Dynamics Observatory, a new dataset, with several hundreds of macrospicules, was constructed encompassing a period of observations over six years. Here, we analyse the measured properties and relations between these properties of macrospicules as function of time during the observed time interval. We found that cross-correlations of several of these macrospicule properties display a strong oscillatory pattern. Next, wavelet analysis is used to provide more detailed information about the temporal behaviour of the various properties of MS. For coronal hole macrospicules, a significant peak is found at around 2-year period. This peak also exists partially or is shifted to longer period, in the case of quiet Sun macrospicules. These observed findings may be rooted in the underlying mechanism generating the solar magnetic field, i.e. the global solar dynamo.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.05.027
  • Model of a fluxtube with a twisted magnetic field in the stratified solar
    • Authors: S. Sen; A. Mangalam
      Pages: 617 - 627
      Abstract: Publication date: 15 January 2018
      Source:Advances in Space Research, Volume 61, Issue 2
      Author(s): S. Sen, A. Mangalam
      We build a single vertical straight magnetic fluxtube spanning the solar photosphere and the transition region which does not expand with height. We assume that the fluxtube containing twisted magnetic fields is in magnetohydrostatic equilibrium within a realistic stratified atmosphere subject to solar gravity. Incorporating specific forms of current density and gas pressure in the Grad–Shafranov equation, we solve the magnetic flux function, and find it to be separable with a Coulomb wave function in radial direction while the vertical part of the solution decreases exponentially. We employ improved fluxtube boundary conditions and take a realistic ambient external pressure for the photosphere to transition region, to derive a family of solutions for reasonable values of the fluxtube radius and magnetic field strength at the base of the axis that are the free parameters in our model. We find that our model estimates are consistent with the magnetic field strength and the radii of Magnetic bright points (MBPs) as estimated from observations. We also derive thermodynamic quantities inside the fluxtube.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.05.032
  • Kelvin–Helmholtz instability in a twisting solar polar coronal hole
           jet observed by SDO/AIA
    • Authors: I. Zhelyazkov; T.V. Zaqarashvili; L. Ofman; R. Chandra
      Pages: 628 - 638
      Abstract: Publication date: 15 January 2018
      Source:Advances in Space Research, Volume 61, Issue 2
      Author(s): I. Zhelyazkov, T.V. Zaqarashvili, L. Ofman, R. Chandra
      We investigate the conditions under which the fluting ( m = 2 ), m = 3 , and m = 12 magnetohydrodynamic (MHD) modes in a uniformly twisted flux tube moving along its axis become unstable in order to model the Kelvin–Helmholtz (KH) instability in a twisting solar coronal hole jet near the northern pole of the Sun. We employed the dispersion relations of MHD modes derived from the linearized MHD equations. We assumed real wavenumbers and complex angular wave frequencies, namely complex wave phse velocities. The dispersion relations were solved numerically at fixed input parameters (taken from observational data) and varying degrees of torsion of the internal magnetic field. It is shown that the stability of the modes depends upon five parameters: the density contrast between the flux tube and its environment, the ratio of the external and internal axial magnetic fields, the twist of the magnetic field lines inside the tube, the ratio of transverse and axial jet’s velocities, and the value of the Alfvén Mach number (the ratio of the tube axial velocity to Alfvén speed inside the flux tube). Using a twisting jet of 2010 August 21 by SDO/AIA and other observations of coronal jets we set the parameters of our theoretical model and have obtained that in a twisted magnetic flux tube of radius of 9.8 Mm, at a density contrast of 0.474 and fixed Alfvén Mach number of ≅ 0.76 , for the three MHD modes there exist instability windows whose width crucially depends upon the internal magnetic field twist. It is found that for the considered modes an azimuthal magnetic field of 1.3 – 1.4 G (computed at the tube boundary) makes the width of the instability windows equal to zero, that is, it suppress the KH instability onset. On the other hand, the times for developing KH instability of the m = 12 MHD mode at instability wavelengths between 15 and 12Mm turn out to be in the range of 1.9 – 4.7 min that is in agreement with the growth rates estimated from the temporal evolution of the observed unstable jet’s blobs in their initial stage.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.06.003
  • Non-stationarity and cross-correlation effects in the MHD solar activity
    • Authors: S.A. Demin; Y.A. Nefedyev; A.O. Andreev; N.Y. Demina; S.F. Timashev
      Pages: 639 - 644
      Abstract: Publication date: 15 January 2018
      Source:Advances in Space Research, Volume 61, Issue 2
      Author(s): S.A. Demin, Y.A. Nefedyev, A.O. Andreev, N.Y. Demina, S.F. Timashev
      The analysis of turbulent processes in sunspots and pores which are self-organizing long-lived magnetic structures is a complicated and not yet solved problem. The present work focuses on studying such magneto-hydrodynamic (MHD) formations on the basis of flicker-noise spectroscopy using a new method of multi-parametric analysis. The non-stationarity and cross-correlation effects taking place in solar activity dynamics are considered. The calculated maximum values of non-stationarity factor may become precursors of significant restructuring in solar magnetic activity. The introduced cross-correlation functions enable us to judge synchronization effects between the signals of various solar activity indicators registered simultaneously.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.06.055
  • Excitation of flare-induced waves in coronal loops and the effects of
           radiative cooling
    • Authors: Elena Provornikova; Leon Ofman; Tongjiang Wang
      Pages: 645 - 654
      Abstract: Publication date: 15 January 2018
      Source:Advances in Space Research, Volume 61, Issue 2
      Author(s): Elena Provornikova, Leon Ofman, Tongjiang Wang
      EUV imaging observations from several space missions (SOHO/EIT, TRACE, and SDO/AIA) have revealed a presence of propagating intensity disturbances in solar coronal loops. These disturbances are typically interpreted as slow magnetoacoustic waves. However, recent spectroscopic observations with Hinode/EIS of active region loops revealed that the propagating intensity disturbances are associated with intermittent plasma upflows (or jets) at the footpoints which are presumably generated by magnetic reconnection. For this reason, whether these disturbances are waves or periodic flows is still being studied. This study is aimed at understanding the physical properties of observed disturbances by investigating the excitation of waves by hot plasma injections from below and the evolution of flows and wave propagation along the loop. We expand our previous studies based on isothermal 3D MHD models of an active region to a more realistic model that includes full energy equation accounting for the effects of radiative losses. Computations are initialized with an equilibrium state of a model active region using potential (dipole) magnetic field, gravitationally stratified density and temperature obtained from the polytropic equation of state. We model an impulsive injection of hot plasma into the steady plasma outflow along the loops of different temperatures, warm (∼1MK) and hot (∼6MK). The simulations show that hot jets launched at the coronal base excite slow magnetoacoustic waves that propagate to high altitudes along the loops, while the injected hot flows decelerate rapidly with heights. Our results support that propagating disturbances observed in EUV are mainly the wave features. We also find that the effect of radiative cooling on the damping of slow-mode waves in 1–6MK coronal loops is small, in agreement with the previous conclusion based on 1D MHD models.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.07.042
  • A study of acoustic halos in active region NOAA 11330 using multi-height
           SDO observations
    • Authors: S.C. Tripathy; K. Jain; S. Kholikov; F. Hill; S.P. Rajaguru; P.S. Cally
      Pages: 691 - 704
      Abstract: Publication date: 15 January 2018
      Source:Advances in Space Research, Volume 61, Issue 2
      Author(s): S.C. Tripathy, K. Jain, S. Kholikov, F. Hill, S.P. Rajaguru, P.S. Cally
      We analyze data from the Helioseismic Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA) instruments on board the Solar Dynamics Observatory (SDO) to characterize the spatio-temporal acoustic power distribution in active regions as a function of the height in the solar atmosphere. For this, we use Doppler velocity and continuum intensity observed using the magnetically sensitive line at 6173 Å as well as intensity at 1600 Å and 1700 Å. We focus on the power enhancements seen around AR 11330 as a function of wave frequency, magnetic field strength, field inclination and observation height. We find that acoustic halos occur above the acoustic cutoff frequency and extends up to 10 mHz in HMI Doppler and AIA 1700 Å observations. Halos are also found to be strong functions of magnetic field and their inclination angle. We further calculate and examine the spatially averaged relative phases and cross-coherence spectra and find different wave characteristics at different heights.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.10.033
  • A study of a long duration B9 flare-CME event and associated shock
    • Authors: R. Chandra; P.F. Chen; A. Fulara; A.K. Srivastava; W. Uddin
      Pages: 705 - 714
      Abstract: Publication date: 15 January 2018
      Source:Advances in Space Research, Volume 61, Issue 2
      Author(s): R. Chandra, P.F. Chen, A. Fulara, A.K. Srivastava, W. Uddin
      We present and discuss here the observations of a small long duration GOES B-class flare associated with a quiescent filament eruption, a global EUV wave and a CME on 2011 May 11. The event was well observed by the Solar Dynamics Observatory (SDO), GONG H α , STEREO and Culgoora spectrograph. As the filament erupted, ahead of the filament we observed the propagation of EIT wave fronts, as well as two flare ribbons on both sides of the polarity inversion line (PIL) on the solar surface. The observations show the co-existence of two types of EUV waves, i.e., a fast and a slow one. A type II radio burst with up to the third harmonic component was also associated with this event. The evolution of photospheric magnetic field showed flux emergence and cancellation at the filament site before its eruption.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.10.034
  • An analytical model of prominence dynamics
    • Authors: Swati Routh; Snehanshu Saha; Atul Bhat; M.N. Sundar
      Pages: 715 - 719
      Abstract: Publication date: 15 January 2018
      Source:Advances in Space Research, Volume 61, Issue 2
      Author(s): Swati Routh, Snehanshu Saha, Atul Bhat, M.N. Sundar
      Solar prominences are magnetic structures incarcerating cool and dense gas in an otherwise hot solar corona. Prominences can be categorized as quiescent and active. Their origin and the presence of cool gas ( ∼ 10 4  K) within the hot ( ∼ 10 6 K ) solar corona remains poorly understood. The structure and dynamics of solar prominences was investigated in a large number of observational and theoretical (both analytical and numerical) studies. In this paper, an analytic model of quiescent solar prominence is developed and used to demonstrate that the prominence velocity increases exponentially, which means that some gas falls downward towards the solar surface, and that Alfvén waves are naturally present in the solar prominences. These theoretical predictions are consistent with the current observational data of solar quiescent prominences.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.10.035
  • Topological and statistical properties of nonlinear force-free fields
    • Authors: A. Mangalam; A. Prasad
      Pages: 738 - 748
      Abstract: Publication date: 15 January 2018
      Source:Advances in Space Research, Volume 61, Issue 2
      Author(s): A. Mangalam, A. Prasad
      We use our semi-analytic solution of the nonlinear force-free field equation to construct three-dimensional magnetic fields that are applicable to the solar corona and study their statistical properties for estimating the degree of braiding exhibited by these fields. We present a new formula for calculating the winding number and compare it with the formula for the crossing number. The comparison is shown for a toy model of two helices and for realistic cases of nonlinear force-free fields; conceptually the formulae are nearly the same but the resulting distributions calculated for a given topology can be different. We also calculate linkages, which are useful topological quantities that are independent measures of the contribution of magnetic braiding to the total free energy and relative helicity of the field. Finally, we derive new analytical bounds for the free energy and relative helicity for the field configurations in terms of the linking number. These bounds will be of utility in estimating the braided energy available for nano-flares or for eruptions.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.11.007
  • Science objectives of the magnetic field experiment onboard Aditya-L1
    • Authors: Vipin K. Yadav; Nandita Srivastava; S.S. Ghosh; P.T. Srikar; Krishnamoorthy Subhalakshmi
      Pages: 749 - 758
      Abstract: Publication date: 15 January 2018
      Source:Advances in Space Research, Volume 61, Issue 2
      Author(s): Vipin K. Yadav, Nandita Srivastava, S.S. Ghosh, P.T. Srikar, Krishnamoorthy Subhalakshmi
      The Aditya-L1 is first Indian solar mission scheduled to be placed in a halo orbit around the first Lagrangian point (L1) of Sun-Earth system in the year 2018–19. The approved scientific payloads onboard Aditya-L1 spacecraft includes a Fluxgate Digital Magnetometer (FGM) to measure the local magnetic field which is necessary to supplement the outcome of other scientific experiments onboard. The in-situ vector magnetic field data at L1 is essential for better understanding of the data provided by the particle and plasma analysis experiments, onboard Aditya-L1 mission. Also, the dynamics of Coronal Mass Ejections (CMEs) can be better understood with the help of in-situ magnetic field data at the L1 point region. This data will also serve as crucial input for the short lead-time space weather forecasting models. The proposed FGM is a dual range magnetic sensor on a 6 m long boom mounted on the Sun viewing panel deck and configured to deploy along the negative roll direction of the spacecraft. Two sets of sensors (tri-axial each) are proposed to be mounted, one at the tip of boom (6 m from the spacecraft) and other, midway (3 m from the spacecraft). The main science objective of this experiment is to measure the magnitude and nature of the interplanetary magnetic field (IMF) locally and to study the disturbed magnetic conditions and extreme solar events by detecting the CME from Sun as a transient event. The proposed secondary science objectives are to study the impact of interplanetary structures and shock solar wind interaction on geo-space environment and to detect low frequency plasma waves emanating from the solar corona at L1 point. This will provide a better understanding on how the Sun affects interplanetary space. In this paper, we shall give the main scientific objectives of the magnetic field experiment and brief technical details of the FGM onboard Aditya-1 spacecraft.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.11.008
  • Investigation of the relationship between ionospheric foF2 and earthquakes
    • Authors: Tuba Karaboga; Murat Canyilmaz; Osman Ozcan
      Abstract: Publication date: Available online 3 February 2018
      Source:Advances in Space Research
      Author(s): Tuba Karaboga, Murat Canyilmaz, Osman Ozcan
      Variations of the ionospheric F2 region critical frequency (foF2) have been investigated statistically before earthquakes during 1980–2008 periods in Japan area. Ionosonde data was taken from Kokubunji station which is in the earthquake preparation zone for all earthquakes. Standard Deviations and Inter-Quartile Range methods are applied to the foF2 data. It is observed that there are anomalous variations in foF2 before earthquakes. These variations can be regarded as ionospheric precursors and may be used for earthquake prediction.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.015
  • CryoSat-2 range, datation and interferometer calibration with Svalbard
    • Authors: Albert Garcia-Mondéjar; Marco Fornari; Jerome Bouffard; Pierre Féménias; Mònica Roca
      Abstract: Publication date: Available online 3 February 2018
      Source:Advances in Space Research
      Author(s): Albert Garcia-Mondéjar, Marco Fornari, Jerome Bouffard, Pierre Féménias, Mònica Roca
      Transponders are commonly used to calibrate absolute range from conventional altimeter waveforms because of their characteristic point target radar reflection. The waveforms corresponding to the transponder distinguish themselves from the other waveforms resulting from natural targets, in power and shape. ESA deployed a transponder available for the CryoSat mission (a refurbished ESA transponder developed for the ERS-1 altimeter calibration). It is deployed at the KSAT Svalbard station: SvalSAT. The transponder is used to calibrate SIRAL’s range, datation, and interferometric phase (or angle of arrival) to meet the mission requirements. In these calibrations, 3 different types of data have been used: the raw Full Bit Rate data, the stack beams before they are multi-looked (stack data) in the Level 1b processor, and the Level 1b data itself. Ideally, the comparison between the theoretical values provided by the well-known target, and the measurement by the instrument to be calibrated provides us with the error that the instrument is introducing when performing its measurement. When this error can be assumed to be constant regardless the conditions, it will provide the bias of the instrument. If the measurements can be repeated after a certain period of time, it can also provide an indication of the instrument drift. This paper presents the method to estimate the range, datation and angle-of-arrival errors from the transponder data and applies it to six years of Baseline C data to derive potential biases and drifts.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.008
  • Satellite capture as a restricted 2+2 body problem
    • Authors: Wafaa Kanaan; David Farrelly; Víctor Lanchares
      Abstract: Publication date: Available online 3 February 2018
      Source:Advances in Space Research
      Author(s): Wafaa Kanaan, David Farrelly, Víctor Lanchares
      A restricted 2 + 2 body problem is proposed as a possible mechanism to explain the capture of small bodies by a planet. In particular, we consider two primaries revolving in a circular mutual orbit and two small bodies of equal mass, neither of which affects the motion of the primaries. If the small bodies are temporarily captured in the Hill sphere of the smaller primary, they may get close enough to each other to exchange energy in such a way that one of them becomes permanently captured. Numerical simulations show that capture is possible for both prograde and retrograde orbits.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.030
  • Obstacle Avoidance Handling and Mixed Integer Predictive Control for Space
    • Authors: Lijun Zong; Jianjun Luo; Mingming Wang; Jianping Yuan
      Abstract: Publication date: Available online 3 February 2018
      Source:Advances in Space Research
      Author(s): Lijun Zong, Jianjun Luo, Mingming Wang, Jianping Yuan
      This paper presents a novel obstacle avoidance constraint and a mixed integer predictive control (MIPC) method for space robots avoiding obstacles and satisfying physical limits during performing tasks. Firstly, a novel kind of obstacle avoidance constraint of space robots, which needs the assumption that the manipulator links and the obstacles can be represented by convex bodies, is proposed by limiting the relative velocity between two closest points which are on the manipulator and the obstacle, respectively. Furthermore, the logical variables are introduced into the obstacle avoidance constraint, which have realized the constraint form is automatically changed to satisfy different obstacle avoidance requirements in different distance intervals between the space robot and the obstacle. Afterwards, the obstacle avoidance constraint and other system physical limits, such as joint angle ranges, the amplitude boundaries of joint velocities and joint torques, are described as inequality constraints of a quadratic programming (QP) problem by using the model predictive control (MPC) method. To guarantee the feasibility of the obtained multi-constraint QP problem, the constraints are treated as soft constraints and assigned levels of priority based on the propositional logic theory, which can realize that the constraints with lower priorities are always firstly violated to recover the feasibility of the QP problem. Since the logical variables have been introduced, the optimization problem including obstacle avoidance and system physical limits as prioritized inequality constraints is termed as MIPC method of space robots, and its computational complexity as well as possible strategies for reducing calculation amount are analyzed. Simulations of the space robot unfolding its manipulator and tracking the end-effector’s desired trajectories with the existence of obstacles and physical limits are presented to demonstrate the effectiveness of the proposed obstacle avoidance strategy and MIPC control method of space robots.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.025
  • Prospects of Using a Permanent Magnetic End Effector to Despin and
           Detumble an Uncooperative Target
    • Authors: Xiaoguang Liu; Yong Lu; Yu Zhou; Yuanhao Yin
      Abstract: Publication date: Available online 2 February 2018
      Source:Advances in Space Research
      Author(s): Xiaoguang Liu, Yong Lu, Yu Zhou, Yuanhao Yin
      Space debris, such as defunct satellites and upper stages of rockets, becomes an uncooperative target after losing its attitude control and communication ability. In addition, tumbling motion can occur due to environmental perturbations and residual angular momentum prior to the object’s end-of-mission. To minimize the collision risk during docking and capturing of the tumbling target, a non-contact method based on the eddy current effect is put forward to transmit the control torque to the tumbling target. The main idea is to induce a controllable torque on the conducting surface of the tumbling target using a rotational magnetic field generated by a Halbach rotor. The radial and axial Halbach rotors are used to damp the spinning and nutation motions of the target, respectively. The normal and tangential force are evaluated concerning the relative pose between the chaser and the target. A simplified dynamic model of the nutation damping and despinning processes is developed and the influences of the asymmetrical principal moments of inertia and transverse angular velocity are discussed. The numerical simulation results show that the designed Halbach rotor stabilized the target attitude within an acceptable time. The electromagnetic nutation damping and despinning method provides new solutions for the development of on-orbit capture technology.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.033
  • Characteristics and Performance Evaluation of Galileo On-orbit Satellites
           Atomic Clocks during 2014-2017
    • Authors: Guanwen Huang; Bobin Cui; Yan Xu; Qin Zhang
      Abstract: Publication date: Available online 2 February 2018
      Source:Advances in Space Research
      Author(s): Guanwen Huang, Bobin Cui, Yan Xu, Qin Zhang
      The on-orbit characteristics and service performance of Galileo navigation system (Galileo) has been drawn attentions since Galileo is the only one global navigation system which is normally equipped with large-scale, high precision and performance hydrogen atomic clocks. Based on a period of 1000 days’ Galileo satellite clock offset products, this article analyzed the performance changes of Galileo satellite clocks when the working clock is switched to the backup clock. The onboard clock phases, frequencies, frequency drifts, the polynomial fitting residuals and the stabilities have been obtained. Results show that the frequency drifts of Galileo satellite clocks can reach up to a magnitude of 10-19 and the fitting precisions are superior to 0.3 ns, while the stabilities in the time length of ten thousand seconds can achieve 10-14. These mainly can be due to the onboard high performance and precision hydrogen atomic clocks.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.034
  • Model Based Computerized Ionospheric Tomography in Space and Time
    • Authors: Hakan Tuna; Orhan Arikan; Feza Arikan
      Abstract: Publication date: Available online 2 February 2018
      Source:Advances in Space Research
      Author(s): Hakan Tuna, Orhan Arikan, Feza Arikan
      Reconstruction of the ionospheric electron density distribution in space and time not only provide basis for better understanding the physical nature of the ionosphere, but also provide improvements in various applications including HF communication. Recently developed IONOLAB-CIT technique provides physically admissible 3D model of the ionosphere by using both Slant Total Electron Content (STEC) measurements obtained from a GPS satellite - receiver network and IRI-Plas model. IONOLAB-CIT technique optimizes IRI-Plas model parameters in the region of interest such that the synthetic STEC computations obtained from the IRI-Plas model are in accordance with the actual STEC measurements. In this work, the IONOLAB-CIT technique is extended to provide reconstructions both in space and time. This extension exploits the temporal continuity of the ionosphere to provide more reliable reconstructions with a reduced computational load. The proposed 4D-IONOLAB-CIT technique is validated on real measurement data obtained from TNPGN-Active GPS receiver network in Turkey.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.031
  • Waveform-based spaceborne GNSS-R wind speed observation: Demonstration and
           analysis using UK TechDemoSat-1 data
    • Authors: Feng Wang; Dongkai Yang; Bo Zhang; Weiqiang Li
      Abstract: Publication date: Available online 1 February 2018
      Source:Advances in Space Research
      Author(s): Feng Wang, Dongkai Yang, Bo Zhang, Weiqiang Li
      This paper explores two types of mathematical functions to fit single- and full-frequency waveform of spaceborne Global Navigation Satellite System-Reflectometry (GNSS-R), respectively. The metrics of the waveforms, such as the noise floor, peak magnitude, mid-point position of the leading edge, leading edge slope and trailing edge slope, can be derived from the parameters of the proposed models. Because the quality of the UK TDS-1 data is not at the level required by remote sensing mission, the waveforms buried in noise or from ice/land are removed by defining peak-to-mean ratio, cosine similarity of the waveform before wind speed are retrieved. The single-parameter retrieval models are developed by comparing the peak magnitude, leading edge slope and trailing edge slope derived from the parameters of the proposed models with in situ wind speed from the ASCAT scatterometer. To improve the retrieval accuracy, three types of multi-parameter observations based on the principle component analysis (PCA), minimum variance (MV) estimator and Back Propagation (BP) network are implemented. The results indicate that compared to the best results of the single-parameter observation, the approaches based on the principle component analysis and minimum variance could not significantly improve retrieval accuracy, however, the BP networks obtain improvement with the RMSE of 2.55 m/s and 2.53 m/s for single- and full-frequency waveform, respectively.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.013
  • Analysis of the carrier-phase multipath in GNSS triple-frequency
           observation combinations
    • Authors: Wang Gao; Xiaolin Meng; Chengfa Gao; Shuguo Pan; Zhuangsheng Zhu; Yan Xia
      Abstract: Publication date: Available online 1 February 2018
      Source:Advances in Space Research
      Author(s): Wang Gao, Xiaolin Meng, Chengfa Gao, Shuguo Pan, Zhuangsheng Zhu, Yan Xia
      Multi-frequency carrier-phase linear combinations are greatly beneficial to improving the performance of ambiguity resolution (AR), cycle slip correction as well as precise positioning. However, as a limiting factor for further improvements in Global Navigation Satellite System (GNSS) high-precision positioning, the effect of multipath is also accentuated due to the measurement combination. In this paper, with real GPS and BDS triple-frequency observations, we analyse the influence of the carrier-phase multipath in three typical triple-frequency combinations: extra-wide-lane (EWL) combination, ionosphere estimation with ambiguity-corrected EWL/wide-lane (WL) combinations and the geometry-free and ionosphere-free (GIF) combination for narrow-lane (NL) AR. For more intuitive reflection of the influence caused by the carrier-phase multipath, zero-baseline tests with no multipath influence were carried out for comparison. The results from consecutive orbital repeat periods were also used to confirm this influence. Experiments show that for the BDS (1, 4, −5) and GPS (1, −6, 5) EWL combinations, the multipath errors could be combined with the biases of several metres in units of distance and over 0.5 cycles in units of cycles. Therefore in single-epoch EWL AR, besides the empirical precision, the bias caused by carrier-phase multipath should be also fully considered. The coefficients of the ionosphere estimation and GIF model are so large that the multipath errors are accentuated many times. Experiments results indicate that even smoothed or averaged with several hours, the errors of ionosphere estimators could be still over 10 cm; the biases of NL ambiguities with GIF model could be still over 0.5 cycles, especially for BDS GEO satellites.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.019
  • Atomic clock performance and combined clock error prediction for the new
           generation of BeiDou navigation satellites
    • Authors: Dongxia Wang; Rui Guo; Shenghong Xiao; Jie Xin; Tingsong Tang; Yunbin Yuan
      Abstract: Publication date: Available online 1 February 2018
      Source:Advances in Space Research
      Author(s): Dongxia Wang, Rui Guo, Shenghong Xiao, Jie Xin, Tingsong Tang, Yunbin Yuan
      Atomic clocks are the core equipment aboard navigation satellites, and their performances and predictions directly determine PNT accuracy. In this paper, the on-orbit performances and prediction accuracies of atomic clocks used in new generation navigation satellites are evaluated using two-way time synchronization data. First, using clock error data preprocessed based on combined MAD gross error detection, the method used to evaluate satellite clock performance is studied. The results illustrate that gross error can be eliminated effectively and that the performances of the new generation of satellites are improved in comparison with those of regional satellites. The frequency accuracy has been enhanced from 6.91 × 10−12 to 3.29 × 10−12, and daily stability has been enhanced from 4.036 × 10−14 to 2.339 × 10−14. Second, a weighted combined clock error prediction model was designed that synthesizes polynomial and gray models using the classical weighted method. The results using the combined models show that the prediction accuracies of the new generation satellites are improved by a factor of two when compared with those for regional satellites, and the mean prediction was enhanced was from 0.77 ns to 0.38 ns. Moreover, from the research findings, it was found that prediction accuracy is significantly correlated with daily stability and frequency accuracy and has a micro-correlation with daily drift rate. Finally, in order to study the prediction accuracies of the new generation of satellites, we studied ISL and concluded that it has greatly increased the measured arc of the MEO satellites and can improve re-entry prediction accuracies from 3–4 ns to 1 ns.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.020
  • Electric potential structures of auroral acceleration region border from
           multi-spacecraft Cluster data
    • Authors: S. Sadeghi; M.R. Emami
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Space Research
      Author(s): S. Sadeghi, M.R. Emami
      This paper studies an auroral event using data from three spacecraft of the Cluster mission, one inside and two at the poleward edge of the bottom of the Auroral Acceleration Region (AAR). The study reveals the three-dimensional profile of the region’s poleward boundary, showing spatial segmentation of the electric potential structures and their decay in time. It also depicts localized magnetic field variations and field-aligned currents that appear to have remained stable for at least 80 s. Such observations became possible due to the fortuitous motion of the three spacecraft nearly parallel to each other and tangential to the AAR edge, so that the differences and variations can be seen when the spacecraft enter and exit the segmentations, hence revealing their position with respect to the AAR.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.024
  • A new interpretation of the historical records of observing Venus in
           daytime with naked eye: Focusing on the meteorological factors in the
           astronomical observation records
    • Authors: Junhyeok Jeon; Young-Joo Kwon; Yong-Sam Lee
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Space Research
      Author(s): Junhyeok Jeon, Young-Joo Kwon, Yong-Sam Lee
      Observing Venus during the daytime is challenging. However, observational data of Venus during the daytime can be found in history books from East Asian countries such as Korea, China and Japan. In this study, we are focused on data from Korean history book, and using records left in the Joseon wangjo sillok, one of the Korean history books from the Joseon dynasty (CE 1392-1910), tries to prove whether the reported observations were actual observation data. We collected these 4,663 records from the Joseon wangjo sillok to determine whether they were actual observations, and to confirm the scientific validity of the records. When we looked at the distribution of observations on a yearly basis, we noticed that there were more observations in the fall and winter, while there were only limited numbers of observations in the spring. This difference in distribution suggests that observations were strongly affected by atmospheric conditions due to the weather. From the 4,663 data collected, we found a cycle of about 1.6 years. The cycle of about 1.6 years is assumed to be related to the conjunction cycle of Venus. And, we found a cycle of about 1.0 years. The cycle of about 1.0 years is assumed to reflect the indirect effects of the Asian dust phenomenon. Our research result verified the record as actual observational data. In addition, this result verified that meteorological factors were involved in the recorded astronomical observation data. We think that our data can be helpful to climate studies on the natural sources of key climate-affecting aerosols.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.028
  • Low-energy near Earth asteroid capture using Earth flybys and aerobraking
    • Authors: Minghu Tan; Colin McInnes; Matteo Ceriotti
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Space Research
      Author(s): Minghu Tan, Colin McInnes, Matteo Ceriotti
      Since the Sun-Earth libration points L1 and L2 are regarded as ideal locations for space science missions and candidate gateways for future crewed interplanetary missions, capturing near-Earth asteroids (NEAs) around the Sun-Earth L1/L2 points has generated significant interest. Therefore, this paper proposes the concept of coupling together a flyby of the Earth and then capturing small NEAs onto Sun–Earth L1/L2 periodic orbits. In this capture strategy, the Sun-Earth circular restricted three-body problem (CRTBP) is used to calculate target Lypaunov orbits and their invariant manifolds. A periapsis map is then employed to determine the required perigee of the Earth flyby. Moreover, depending on the perigee distance of the flyby, Earth flybys with and without aerobraking are investigated to design a transfer trajectory capturing a small NEA from its initial orbit to the stable manifolds associated with Sun-Earth L1/L2 periodic orbits. Finally, a global optimization is carried out, based on a detailed design procedure for NEA capture using an Earth flyby. Results show that the NEA capture strategies using an Earth flyby with and without aerobraking both have the potential to be of lower cost in terms of energy requirements than a direct NEA capture strategy without the Earth flyby. Moreover, NEA capture with an Earth flyby also has the potential for a shorter flight time compared to the NEA capture strategy without the Earth flyby.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.027
  • Novel active driven drop tower facility for microgravity experiments
           investigating production technologies on the example of substrate-free
           additive manufacturing
    • Authors: Christoph Lotz; Yvonne Wessarges; Jörg Hermsdorf; Wolfgang Ertmer; Ludger Overmeyer
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Space Research
      Author(s): Christoph Lotz, Yvonne Wessarges, Jörg Hermsdorf, Wolfgang Ertmer, Ludger Overmeyer
      Through the striving of humanity into space, new production processes and technologies for the use under microgravity will be essential in the future. Production of objects in space demands for new processes, like additive manufacturing. This paper presents the concept and the realization for a new machine to investigate microgravity production processes on earth. The machine is based on linear long stator drives and a vacuum chamber carrying up to 1,000 kg. For the first time high repetition rate and associated low experimental costs can provide basic research. The paper also introduces the substrate-free additive manufacturing as a future research topic and one of our primary application.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.010
  • Arctide2017, A High-Resolution Regional Tidal Model in the Arctic Ocean
    • Authors: M. Cancet; O.B. Andersen; F. Lyard; D. Cotton; J. Benveniste
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Space Research
      Author(s): M. Cancet, O.B. Andersen, F. Lyard, D. Cotton, J. Benveniste
      The Arctic Ocean is a challenging region for tidal modelling. The accuracy of the global tidal models decreases by several centimeters in the Polar Regions, which has a large impact on the quality of the satellite altimeter sea surface heights and the altimetry-derived products. NOVELTIS, DTU Space and LEGOS have developed Arctide2017, a regional, high-resolution tidal atlas in the Arctic Ocean, in the framework of an extension of the CryoSat Plus for Ocean (CP4O) ESA STSE (Support to Science Element) project. In particular, this atlas benefits from the assimilation of the most complete satellite altimetry dataset ever used in this region, including Envisat data up to 82°N and CryoSat-2 data between 82°N and 88°N. The combination of these satellite altimetry missions gives the best possible coverage of altimetry-derived tidal constituents. The available tide gauge data were also used for data assimilation and validation. This paper presents the implementation methodology and the performance of this new regional tidal model in the Arctic Ocean, compared to the existing global and regional tidal models.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.007
  • Precision analysis of autonomous orbit determination using star sensor for
           Beidou MEO satellite
    • Authors: Lin Shang; Jiachao Chang; Jun Zhang; Guotong Li
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Space Research
      Author(s): Lin Shang, Jiachao Chang, Jun Zhang, Guotong Li
      This paper focuses on the autonomous orbit determination accuracy of Beidou MEO satellite using the onboard observations of the star sensors and infrared horizon sensor. A polynomial fitting method is proposed to calibrate the periodic error in the observation of the infrared horizon sensor, which will greatly influence the accuracy of autonomous orbit determination. Test results show that the periodic error can be eliminated using the polynomial fitting method. The User Range Error (URE) of Beidou MEO satellite is less than 2 km using the observations of the star sensors and infrared horizon sensor for autonomous orbit determination. The error of the Right Ascension of Ascending Node (RAAN) is less than 60  μ rad and the observations of star sensors can be used as a spatial basis for Beidou MEO navigation constellation.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.017
  • Optimization of fault-tolerant thruster configurations for satellite
    • Authors: Yasuhiro Yoshimura; Hirohisa Kojima
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Space Research
      Author(s): Yasuhiro Yoshimura, Hirohisa Kojima
      The fault tolerance of spacecraft actuators significantly affects the reliability of satellites and the likelihood of successful missions. To enhance the fault tolerance of the actuators, this study derives optimal fault-tolerant configurations of fixed thrusters that maximize the controllability of a fully-actuated or underactuated satellite. The proposed method optimizes thrust and torque directions generated by the thrusters. Thus a cost function in terms of the thruster locations and directions is defined as the summation of the generated control forces and torques with respect to the body-fixed frame. The optimal configuration is obtained by the successive use of an energy potential method that is motivated by Thomson’s problem. Some numerical examples are provided that show the effectiveness of the proposed formulation and optimization method.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.014
  • Optimal Trajectory Planning of Free-Floating Space Manipulator Using
           Differential Evolution Algorithm
    • Authors: Mingming Wang; Jianjun Luo; Jing Fang; Jianping Yuan
      Abstract: Publication date: Available online 16 January 2018
      Source:Advances in Space Research
      Author(s): Mingming Wang, Jianjun Luo, Jing Fang, Jianping Yuan
      The existence of the path dependent dynamic singularities limits the volume of available workspace of free-floating space robot and induces enormous joint velocities when such singularities are met. In order to overcome this demerit, this paper presents an optimal joint trajectory planning method using forward kinematics equations of free-floating space robot, while joint motion laws are delineated with application of the concept of reaction null-space. Bézier curve, in conjunction with the null-space column vectors, are applied to describe the joint trajectories. Considering the forward kinematics equations of the free-floating space robot, the trajectory planning issue is consequently transferred to an optimization issue while the control points to construct the Bézier curve are the design variables. A constrained differential evolution (DE) scheme with premature handling strategy is implemented to find the optimal solution of the design variables while specific objectives and imposed constraints are satisfied. Differ from traditional methods, we synthesize null-space and specialized curve to provide a novel viewpoint for trajectory planning of free-floating space robot. Simulation results are presented for trajectory planning of 7 degree-of-freedom (DOF) kinematically redundant manipulator mounted on a free-floating spacecraft and demonstrate the feasibility and effectiveness of the proposed method.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.011
  • From conventional to Delay Doppler altimetry: A demonstration of
           continuity and improvements with the Cryosat-2 mission
    • Authors: M. Raynal; S. Labroue; T. Moreau; F. Boy; N. Picot
      Abstract: Publication date: Available online 16 January 2018
      Source:Advances in Space Research
      Author(s): M. Raynal, S. Labroue, T. Moreau, F. Boy, N. Picot
      Cryosat-2 is the first satellite that embarks an altimeter able to operate in several modes. Among them, the Synthetic Aperture Radar mode (SARM) also referred to as Delay Doppler mode is expected to improve the measurement resolution and precision. Based on a two year time series, this paper presents the SARM assessment over ocean. It demonstrates the seamless transition, below the centimeter level, between conventional pulse-limited and Delay Doppler altimetry at long wavelength for the sea level. Nevertheless, the SARM retrieved Significant Wave Height (SWH) is biased by 20 cm and depends on the sea state. This paper also confirms that, thanks to the better signal to noise ratio and along track resolution brought by the SARM, the small scales observability is significantly improved with respect to the Low Resolution Mode (LRM). The SARM Sea Level reveals a spectral slope never observed for wavelength below 30 km that is not yet explained. Further analyses at global scales using the Sentinel-3A dataset will certainly help to characterize the source of this signal.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2018.01.006
  • Bayesian coronal seismology
    • Authors: Arregui
      Abstract: Publication date: 15 January 2018
      Source:Advances in Space Research, Volume 61, Issue 2
      Author(s): Iñigo Arregui
      In contrast to the situation in a laboratory, the study of the solar atmosphere has to be pursued without direct access to the physical conditions of interest. Information is therefore incomplete and uncertain and inference methods need to be employed to diagnose the physical conditions and processes. One of such methods, solar atmospheric seismology, makes use of observed and theoretically predicted properties of waves to infer plasma and magnetic field properties. A recent development in solar atmospheric seismology consists in the use of inversion and model comparison methods based on Bayesian analysis. In this paper, the philosophy and methodology of Bayesian analysis are first explained. Then, we provide an account of what has been achieved so far from the application of these techniques to solar atmospheric seismology and a prospect of possible future extensions.

      PubDate: 2018-02-05T12:23:48Z
  • Fundamental (f) oscillations in a magnetically coupled solar
           interior-atmosphere system – An analytical approach
    • Abstract: Publication date: 15 January 2018
      Source:Advances in Space Research, Volume 61, Issue 2
      Author(s): Balázs Pintér, R. Erdélyi
      Solar fundamental (f) acoustic mode oscillations are investigated analytically in a magnetohydrodynamic (MHD) model. The model consists of three layers in planar geometry, representing the solar interior, the magnetic atmosphere, and a transitional layer sandwiched between them. Since we focus on the fundamental mode here, we assume the plasma is incompressible. A horizontal, canopy-like, magnetic field is introduced to the atmosphere, in which degenerated slow MHD waves can exist. The global (f-mode) oscillations can couple to local atmospheric Alfvén waves, resulting, e.g., in a frequency shift of the oscillations. The dispersion relation of the global oscillation mode is derived, and is solved analytically for the thin-transitional layer approximation and for the weak-field approximation. Analytical formulae are also provided for the frequency shifts due to the presence of a thin transitional layer and a weak atmospheric magnetic field. The analytical results generally indicate that, compared to the fundamental value ( ω = gk ), the mode frequency is reduced by the presence of an atmosphere by a few per cent. A thin transitional layer reduces the eigen-frequencies further by about an additional hundred microhertz. Finally, a weak atmospheric magnetic field can slightly, by a few percent, increase the frequency of the eigen-mode. Stronger magnetic fields, however, can increase the f-mode frequency by even up to ten per cent, which cannot be seen in observed data. The presence of a magnetic atmosphere in the three-layer model also introduces non-permitted propagation windows in the frequency spectrum; here, f-mode oscillations cannot exist with certain values of the harmonic degree. The eigen-frequencies can be sensitive to the background physical parameters, such as an atmospheric density scale-height or the rate of the plasma density drop at the photosphere. Such information, if ever observed with high-resolution instrumentation and inverted, could help to gain further insight into solar magnetic structures by means of solar magneto-seismology, and could provide further insight into the role of magnetism in solar oscillations.

      PubDate: 2018-02-05T12:23:48Z
  • List of Referees
    • Abstract: Publication date: 15 January 2018
      Source:Advances in Space Research, Volume 61, Issue 2

      PubDate: 2018-02-05T12:23:48Z
  • Attitude Control for On-Orbit Servicing Spacecraft Using Hybrid Actuator
    • Authors: Yunhua Wu; Feng Han; Mohong Zheng; Mengjie He; Zhiming Chen; Bing Hua; Feng Wang
      Abstract: Publication date: Available online 11 January 2018
      Source:Advances in Space Research
      Author(s): Yunhua Wu, Feng Han, Mohong Zheng, Mengjie He, Zhiming Chen, Bing Hua, Feng Wang
      On-orbit servicing is one of the research hotspots of space missions. A small satellite equipped with multiple robotic manipulators is expected to carry out device replacement task for target large spacecraft. Attitude hyperstable control of a small satellite platform under rotations of the manipulators is a challenging problem. A hybrid momentum exchanging actuator consists of Control Moment Gyro (CMG) and Reaction Wheel (RW) is proposed to tackle the above issue, due to its huge amount of momentum storage capacity of the CMG and high control accuracy of the RW, in which the CMG produces large command torque while the RW offers additional control degrees. The constructed dynamic model of the servicing satellite advises that it’s feasible for attitude hyperstable control of the platform with arbitrary manipulators through compensating the disturbance generated by rapid rotation of the manipulators. Then, null motion between the CMG and RW is exploited to drive the system to the expected target with favorable performance, and to overcome the CMG inherent geometric singularity and RW saturation. Simulations with different initial situations, including CMG hyperbolic and elliptic singularities and RW saturation, are executed. Compared to the scenarios where the CMG or RW fails stabilizing the platform, large control torque, precise control effect and escape of singularity are guaranteed by the introduced hybrid actuator, CMGRW (CMGRW refers to the hybrid momentum exchanging devices in this paper, consisting of 4 CMGs in classical pyramid cluster and 3 RWs in an orthogonal group (specific description can been found in Section 4).). The feasible performance of the satellite, CMG and RW under large disturbance demonstrates that the control architecture proposed is capable of attitude control for on-orbit servicing satellite with multiple robotic manipulators.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.12.039
  • Didactic satellite based on Android platform for space operation
           demonstration and development
    • Authors: Omar Ben Bahri; Kamel Besbes
      Abstract: Publication date: Available online 11 January 2018
      Source:Advances in Space Research
      Author(s): Omar Ben Bahri, Kamel Besbes
      Space technology plays a pivotal role in society development. It offers new methods for telemetry, monitoring and control. However, this sector requires training, research and skills development but the lack of instruments, materials and budgets affects the ambiguity to understand satellite technology. The objective of this paper is to describe a demonstration prototype of a smart phone device for space operations study. Therefore, the first task was carried out to give a demonstration for spatial imagery and attitude determination missions through a wireless communication. The smart phone’s Bluetooth was used to achieve this goal inclusive of a new method to enable real time transmission. In addition, an algorithm around a quaternion based Kalman filter was included in order to detect the reliability of the prototype's orientation. The second task was carried out to provide a demonstration for the attitude control mission using the smart phone’s orientation sensor, including a new method for an autonomous guided mode. As a result, the acquisition platform showed real time measurement with good accuracy for orientation detection and image transmission. In addition, the prototype kept the balance during the demonstration based on the attitude control method.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.12.040
  • Predictive fault-tolerant control of an all-thruster satellite in 6-DOF
           motion via neural network model updating
    • Authors: M.M. Tavakoli; N. Assadian
      Abstract: Publication date: Available online 11 January 2018
      Source:Advances in Space Research
      Author(s): M.M. Tavakoli, N. Assadian
      The problem of controlling an all-thruster spacecraft in the coupled translational-rotational motion in presence of actuators fault and/or failure is investigated in this paper. The nonlinear model predictive control approach is used because of its ability to predict the future behavior of the system. The fault/failure of the thrusters changes the mapping between the commanded forces to the thrusters and actual force/torque generated by the thruster system. Thus, the basic six degree-of-freedom kinetic equations are separated from this mapping and a set of neural networks are trained off-line to learn the kinetic equations. Then, two neural networks are attached to these trained networks in order to learn the thruster commands to force/torque mappings on-line. Different off-nominal conditions are modeled so that neural networks can detect any failure and fault, including scale factor and misalignment of thrusters. A simple model of the spacecraft relative motion is used in MPC to decrease the computational burden. However, a precise model by the means of orbit propagation including different types of perturbation is utilized to evaluate the usefulness of the proposed approach in actual conditions. The numerical simulation shows that this method can successfully control the all-thruster spacecraft with ON-OFF thrusters in different combinations of thruster fault and/or failure.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.12.032
  • Near real-time PPP-based monitoring of the ionosphere using dual-frequency
           GPS/BDS/Galileo data
    • Authors: Zhinmin Liu; Yangyang Li; Fei Li; Jinyun Guo
      Abstract: Publication date: Available online 10 January 2018
      Source:Advances in Space Research
      Author(s): Zhinmin Liu, Yangyang Li, Fei Li, Jinyun Guo
      Ionosphere delay is very important to GNSS observations, since it is one of the main error sources which have to be mitigated even eliminated in order to determine reliable and precise positions. The ionosphere is a dispersive medium to radio signal, so the value of the group delay or phase advance of GNSS radio signal depends on the signal frequency. Ground-based GNSS stations have been used for ionosphere monitoring and modeling for a long time. In this paper we will introduce a novel approach suitable for single-receiver operation based on the precise point positioning (PPP) technique. One of the main characteristic is that only carrier-phase observations are used to avoid particular effects of pseudorange observations. The technique consists of introducing ionosphere ambiguity parameters obtained from PPP filter into the geometry-free combination of observations to estimate ionospheric delays. Observational data from stations that are capable of tracking the GPS/BDS/GALILEO from the International GNSS Service (IGS) Multi-GNSS Experiments (MGEX) network are processed. For the purpose of performance validation, ionospheric delays series derived from the novel approach are compared with the global ionospheric map (GIM) from Ionospheric Associate Analysis Centers (IAACs). The results are encouraging and offer potential solutions to the near real-time ionosphere monitoring.

      PubDate: 2018-02-05T12:23:48Z
      DOI: 10.1016/j.asr.2017.12.038
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Heriot-Watt University
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