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  Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 124 journals)
Showing 1 - 30 of 30 Journals sorted by number of followers
AIAA Journal     Hybrid Journal   (Followers: 1003)
SpaceNews     Free   (Followers: 779)
Journal of Spacecraft and Rockets     Hybrid Journal   (Followers: 702)
Journal of Propulsion and Power     Hybrid Journal   (Followers: 570)
Aviation Week     Full-text available via subscription   (Followers: 412)
Aerospace Science and Technology     Hybrid Journal   (Followers: 307)
Advances in Space Research     Hybrid Journal   (Followers: 296)
IEEE Transactions on Aerospace and Electronic Systems     Hybrid Journal   (Followers: 281)
Journal of Aircraft     Hybrid Journal   (Followers: 264)
IEEE Aerospace and Electronic Systems Magazine     Full-text available via subscription   (Followers: 251)
Control Systems     Hybrid Journal   (Followers: 235)
Acta Astronautica     Hybrid Journal   (Followers: 220)
Gyroscopy and Navigation     Hybrid Journal   (Followers: 178)
Journal of Navigation     Hybrid Journal   (Followers: 177)
Journal of Guidance, Control, and Dynamics     Hybrid Journal   (Followers: 165)
Aircraft Engineering and Aerospace Technology     Hybrid Journal   (Followers: 139)
Space Science International     Open Access   (Followers: 118)
Space Science Reviews     Hybrid Journal   (Followers: 92)
Propulsion and Power Research     Open Access   (Followers: 89)
International Journal of Aerospace Engineering     Open Access   (Followers: 86)
Progress in Aerospace Sciences     Full-text available via subscription   (Followers: 82)
Advances in Aerospace Engineering     Open Access   (Followers: 74)
Journal of Aerospace Engineering     Full-text available via subscription   (Followers: 66)
Aerospace     Open Access   (Followers: 64)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 57)
Space Safety Magazine     Free   (Followers: 50)
International Journal of Aerodynamics     Hybrid Journal   (Followers: 46)
IEEE Transactions on Circuits and Systems I: Regular Papers     Hybrid Journal   (Followers: 43)
Space Research Today     Full-text available via subscription   (Followers: 43)
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering     Hybrid Journal   (Followers: 42)
International Journal of Aeroacoustics     Hybrid Journal   (Followers: 37)
International Journal of Aerospace Sciences     Open Access   (Followers: 36)
Canadian Aeronautics and Space Journal     Full-text available via subscription   (Followers: 31)
Space Policy     Hybrid Journal   (Followers: 30)
Journal of Space Weather and Space Climate     Open Access   (Followers: 30)
CEAS Aeronautical Journal     Hybrid Journal   (Followers: 30)
Journal of Aerodynamics     Open Access   (Followers: 27)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 27)
Egyptian Journal of Remote Sensing and Space Science     Open Access   (Followers: 25)
Russian Aeronautics (Iz VUZ)     Hybrid Journal   (Followers: 23)
International Journal of Aerospace Innovations     Full-text available via subscription   (Followers: 23)
Aviation Psychology and Applied Human Factors     Hybrid Journal   (Followers: 23)
Aerospace Medicine and Human Performance     Full-text available via subscription   (Followers: 22)
International Journal of Aerospace Psychology     Hybrid Journal   (Followers: 22)
Journal of Aerospace Engineering & Technology     Full-text available via subscription   (Followers: 22)
Journal of Wind Engineering and Industrial Aerodynamics     Hybrid Journal   (Followers: 21)
Artificial Satellites     Open Access   (Followers: 21)
Fatigue of Aircraft Structures     Open Access   (Followers: 21)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 20)
Frontiers in Aerospace Engineering     Open Access   (Followers: 20)
International Journal of Space Structures     Full-text available via subscription   (Followers: 19)
Nonlinear Dynamics     Hybrid Journal   (Followers: 19)
Chinese Journal of Aeronautics     Open Access   (Followers: 19)
Proceedings of the Human Factors and Ergonomics Society Annual Meeting     Hybrid Journal   (Followers: 16)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 15)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 15)
Journal of Aircraft and Spacecraft Technology     Open Access   (Followers: 15)
Advances in Aerospace Science and Technology     Open Access   (Followers: 14)
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 13)
Aviation     Open Access   (Followers: 12)
International Journal of Micro Air Vehicles     Open Access   (Followers: 11)
Journal of Airline and Airport Management     Open Access   (Followers: 11)
Journal of the Astronautical Sciences     Hybrid Journal   (Followers: 11)
International Journal of Space Technology Management and Innovation     Full-text available via subscription   (Followers: 11)
Population Space and Place     Hybrid Journal   (Followers: 10)
Journal of Aviation Technology and Engineering     Open Access   (Followers: 10)
Journal of Aeronautical Materials     Open Access   (Followers: 10)
Aerospace Systems     Hybrid Journal   (Followers: 10)
International Journal of Crashworthiness     Hybrid Journal   (Followers: 10)
Journal of Aerospace Technology and Management     Open Access   (Followers: 10)
Aeronautical Journal, The     Hybrid Journal   (Followers: 9)
Journal of the American Helicopter Society     Full-text available via subscription   (Followers: 9)
International Journal of Aviation, Aeronautics, and Aerospace     Open Access   (Followers: 9)
International Journal of Aviation Technology, Engineering and Management     Full-text available via subscription   (Followers: 8)
Journal of Space Safety Engineering     Hybrid Journal   (Followers: 8)
International Journal of Applied Geospatial Research     Hybrid Journal   (Followers: 7)
Transportmetrica A : Transport Science     Hybrid Journal   (Followers: 7)
Aerospace technic and technology     Open Access   (Followers: 7)
Aviation in Focus - Journal of Aeronautical Sciences     Open Access   (Followers: 7)
New Space     Hybrid Journal   (Followers: 6)
Space and Polity     Hybrid Journal   (Followers: 6)
Aerotecnica Missili & Spazio : Journal of Aerospace Science, Technologies & Systems     Hybrid Journal   (Followers: 6)
Civil Aviation High Technologies     Open Access   (Followers: 6)
Air Medical Journal     Hybrid Journal   (Followers: 6)
REACH - Reviews in Human Space Exploration     Full-text available via subscription   (Followers: 5)
RocketSTEM     Free   (Followers: 5)
International Journal of Sustainable Aviation     Hybrid Journal   (Followers: 5)
Journal of Astrobiology & Outreach     Open Access   (Followers: 5)
Life Sciences in Space Research     Hybrid Journal   (Followers: 5)
International Journal of Aviation Management     Hybrid Journal   (Followers: 5)
Cosmic Research     Hybrid Journal   (Followers: 5)
Journal of Spatial Science     Hybrid Journal   (Followers: 4)
Journal of KONBiN     Open Access   (Followers: 4)
Astrodynamics     Hybrid Journal   (Followers: 4)
International Journal of Aeronautical and Space Sciences     Hybrid Journal   (Followers: 4)
Unmanned Systems     Hybrid Journal   (Followers: 4)
Transport and Aerospace Engineering     Open Access   (Followers: 4)
Open Aerospace Engineering Journal     Open Access   (Followers: 4)
Problemy Mechatroniki. Uzbrojenie, lotnictwo, inżynieria bezpieczeństwa / Problems of Mechatronics. Armament, Aviation, Safety Engineering     Open Access   (Followers: 3)
Microgravity Science and Technology     Hybrid Journal   (Followers: 3)
Journal of the Australasian Society of Aerospace Medicine     Open Access   (Followers: 3)
npj Microgravity     Open Access   (Followers: 3)
ASTRA Proceedings     Open Access   (Followers: 3)
MAD - Magazine of Aviation Development     Open Access   (Followers: 3)
Ciencia y Poder Aéreo     Open Access   (Followers: 3)
Journal of Aviation/Aerospace Education & Research     Open Access   (Followers: 2)
Advances in Astronautics Science and Technology     Hybrid Journal   (Followers: 2)
Journal of Engineering and Technological Sciences     Open Access   (Followers: 2)
IEEE Journal on Miniaturization for Air and Space Systems     Hybrid Journal   (Followers: 2)
Perspectives of Earth and Space Scientists i     Open Access   (Followers: 1)
Investigación Pecuaria     Open Access   (Followers: 1)
Transactions on Aerospace Research     Open Access   (Followers: 1)
Вісник Національного Авіаційного Університету     Open Access   (Followers: 1)
Science and Education : Scientific Publication of BMSTU     Open Access   (Followers: 1)
Spatial Information Research     Hybrid Journal   (Followers: 1)
Xibei Gongye Daxue Xuebao / Journal of Northwestern Polytechnical University     Open Access  
Mekanika : Jurnal Teknik Mesin i     Open Access  

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Similar Journals
Journal Cover
Frontiers in Astronomy and Space Sciences
Number of Followers: 15  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2296-987X
Published by Frontiers Media Homepage  [96 journals]
  • Estimating Inner Magnetospheric Radial Diffusion Using a Hybrid-Vlasov
           Simulation

    • Authors: H. George, A. Osmane, E. K. J. Kilpua, S. Lejosne , L. Turc, M. Grandin, M. M. H. Kalliokoski, S. Hoilijoki, U. Ganse, M. Alho, M. Battarbee, M. Bussov, M. Dubart, A. Johlander, T. Manglayev, K. Papadakis, Y. Pfau-Kempf, J. Suni, V. Tarvus, H. Zhou, M. Palmroth
      Abstract: Radial diffusion coefficients quantify non-adiabatic transport of energetic particles by electromagnetic field fluctuations in planetary radiation belts. Theoretically, radial diffusion occurs for an ensemble of particles that experience irreversible violation of their third adiabatic invariant, which is equivalent to a change in their Roederer L* parameter. Thus, the Roederer L* coordinate is the fundamental quantity from which radial diffusion coefficients can be computed. In this study, we present a methodology to calculate the Lagrangian derivative of L* from global magnetospheric simulations, and test it with an application to Vlasiator, a hybrid-Vlasov model of near-Earth space. We use a Hamiltonian formalism for particles confined to closed drift shells with conserved first and second adiabatic invariants to compute changes in the guiding center drift paths due to electric and magnetic field fluctuations. We investigate the feasibility of this methodology by computing the time derivative of L* for an equatorial ultrarelativistic electron population travelling along four guiding center drift paths in the outer radiation belt during a 5 minute portion of a Vlasiator simulation. Radial diffusion in this simulation is primarily driven by ultralow frequency waves in the Pc3 range (10–45 s period range) that are generated in the foreshock and transmitted through the magnetopause to the outer radiation belt environment. Our results show that an alternative methodology to compute detailed radial diffusion transport is now available and could form the basis for comparison studies between numerical and observational measurements of radial transport in the Earth’s radiation belts.
      PubDate: 2022-05-18T00:00:00Z
       
  • Linear Theory of Electromagnetic Ion Beam Instabilities in the Earth’s
           Forshock: Peter Gary’s Contributions (1981–1991)

    • Authors: Dan Winske, Lynn B. Wilson
      Abstract: We discuss Peter Gary’s contributions to the understanding of the origin and properties of ultra-low frequency (ULF) waves in the Earth’s foreshock during the period when the International Sun Earth Explorer spacecraft (ISEE-1 and -2) provided unique data about the plasma and wave environment in this region. Peter’s work concerning the linear theory of electromagnetic ion beam instabilities is contained in five journal articles and then summarized in a review article, all of which are discussed here. Brief summaries of observations and theory prior to ISEE as well as to later work are also included.
      PubDate: 2022-05-16T00:00:00Z
       
  • The Planetary Nebula Luminosity Function in the Era of Precision Cosmology

    • Authors: Robin Ciardullo
      Abstract: One of the great surprises of the late 1980s was the discovery that the [O III] λ5007 planetary nebula luminosity function (PNLF) could be used as a precision extragalactic standard candle. Despite the lack of any robust theory for the phenomenon, the technique passed a myriad of internal and external tests, and became an extremely reliable tool for obtaining distances to large galaxies within ∼20 Mpc. But in more recent years, the use of the technique has declined, due in part to the changing landscape of cosmology. Here we review the history of the PNLF, the experiments that confirmed its utility, and the reasons why interest in the method faded at the turn of the millennium. We also describe how and why the PNLF is making a comeback, and present some of the method’s recent results. Finally, we discuss how the PNLF must be analyzed in the era of precision cosmology, and detail the issues that must be overcome in order to address the current tension between local measures of the Hubble constant and values derived from the microwave background. If these issues can be understood, then the PNLF can provide a useful cross-check on distance measurements out to ∼40 Mpc.
      PubDate: 2022-05-16T00:00:00Z
       
  • Editorial: Micro- to Macro-Scale Dynamics of Earth’s Flank
           Magnetopause

    • Authors: Kyoung-Joo Hwang, Hiroshi Hasegawa, Katariina Nykyri, Takuma Nakamura, Simon Wing
      PubDate: 2022-05-13T00:00:00Z
       
  • Formamide-Based Post-impact Thermal Prebiotic Synthesis in Simulated
           Craters: Intermediates, Products and Mechanism

    • Authors: Martin Ferus, Antonín Knížek, Lukáš Petera, Adam Pastorek, Jana Hrnčířová, Luboš Jankovič, Ondřej Ivanek, Jiří Šponer, Anna Křivková, Homa Saeidfirozeh, Svatopluk Civiš, Elias Chatzitheodoridis, Klaudia Mráziková, Lukáš Nejdl, Franz Saija, Judit E. Šponer, Giuseppe Cassone
      Abstract: Influx of matter from impacting meteoroids and hydrothermal crater weathering are important factors modifying the rock and mineral inventory of young planets undergoing heavy bombardment. These processes may have influenced not only the geochemical environment of, e.g., early Mars and other planets, but also the peculiar prebiotic chemistry on early Earth. Here, we present a synergistic experimental and computational investigation of the intermediates of chemical reactions of the formamide-based synthesis of canonical and non-canonical nucleobases by thermochemistry in hot hydrothermal crater environments. We put our findings into context with previously investigated plasma-initiated synthesis occuring directly during impact. Both processes result into the formation of all canonical nucleobases, hypoxanthine, purine, and into the onset of the simplest amino acid glycine. Furthermore, it turns out that radical species such as CN and H play a key role in the plasma-assisted impact chemistry. However, post-impact thermochemistry is essential for the origin of formamidine and 2-aminoacetonitrile, intermediate species detected in this study by means of FTIR spectroscopy.
      PubDate: 2022-05-13T00:00:00Z
       
  • From Coronal Holes to Pulsars and Back Again: Learning the Importance of
           Data

    • Authors: Y.-M. Wang
      Abstract: Although wanting to become an astronomer from an early age, I ended up in solar physics purely by chance, after first working in high-energy astrophysics. I’ve never regretted switching from the pulsar to the solar magnetosphere, because solar physics has a great advantage over other areas of astrophysics—in the enormous amount of high-quality data available, much of it underutilized. I’ve often wondered why theoreticians and modelers don’t spent more time looking at these data (perhaps they feel that it is cheating, like taking a peek at the answers to a difficult homework assignment'). Conversely, I wonder why observers and data analysts aren’t more skeptical of the theoretical models—especially the fashionable ones.
      PubDate: 2022-05-12T00:00:00Z
       
  • Multiple E-Region Radar Propagation Modes Measured by the VHF SIMONe
           Norway System During Active Ionospheric Conditions

    • Authors: Devin Huyghebaert, Matthias Clahsen, Jorge L. Chau, Toralf Renkwitz, Ralph Latteck, Magnar G. Johnsen, Juha Vierinen
      Abstract: Multiple propagation modes between different bistatic radar links were measured during the operations of a very high frequency (VHF) 32.55 MHz radar system in northern Norway. The Spread Spectrum Interferometric Multistatic meteor radar Observing Network (SIMONe) Norway system detected meteor trails, direct transmitter to receiver signal propagation, over-the-horizon signal propagation from the SIMONe Germany system, ground and/or sea scatter, and ionospheric scatter on 27 August 2021 between 16:30–20:00 UT. These simultaneous detections were during an active ionospheric period with multiple occurrences of energetic charged particle precipitation. The SIMONe systems used continuous-wave (CW) pseudo-random phase modulated transmit signals and interferometry to make it possible to isolate each of these propagation modes and examine their characteristics. Different multistatic links at three receiver locations were analyzed, providing multistatic measurements of the regions with spatial and temporal resolutions on the order of 1.5 km and 2 s. The analysis techniques are described, with characteristics of the radar signal presented for each propagation mode and multistatic link. This study serves to highlight the capabilities of the SIMONe Norway system to research multiple aspects of ionospheric phenomena, specifically in the lower thermosphere-mesosphere boundary region.
      PubDate: 2022-05-10T00:00:00Z
       
  • Domain-Agnostic Outlier Ranking Algorithms—A Configurable Pipeline for
           Facilitating Outlier Detection in Scientific Datasets

    • Authors: Hannah R. Kerner, Umaa Rebbapragada, Kiri L. Wagstaff, Steven Lu, Bryce Dubayah, Eric Huff, Jake Lee, Vinay Raman, Sakshum Kulshrestha
      Abstract: Automatic detection of outliers is universally needed when working with scientific datasets, e.g., for cleaning datasets or flagging novel samples to guide instrument acquisition or scientific analysis. We present Domain-agnostic Outlier Ranking Algorithms (DORA), a configurable pipeline that facilitates application and evaluation of outlier detection methods in a variety of domains. DORA allows users to configure experiments by specifying the location of their dataset(s), the input data type, feature extraction methods, and which algorithms should be applied. DORA supports image, raster, time series, or feature vector input data types and outlier detection methods that include Isolation Forest, DEMUD, PCA, RX detector, Local RX, negative sampling, and probabilistic autoencoder. Each algorithm assigns an outlier score to each data sample. DORA provides results interpretation modules to help users process the results, including sorting samples by outlier score, evaluating the fraction of known outliers in n selections, clustering groups of similar outliers together, and web visualization. We demonstrated how DORA facilitates application, evaluation, and interpretation of outlier detection methods by performing experiments for three real-world datasets from Earth science, planetary science, and astrophysics, as well as one benchmark dataset (MNIST/Fashion-MNIST). We found that no single algorithm performed best across all datasets, underscoring the need for a tool that enables comparison of multiple algorithms.
      PubDate: 2022-05-10T00:00:00Z
       
  • Exploitation of the IPHAS to Investigate Planetary Nebulae

    • Authors: Laurence Sabin, Jesús A. Toalá, Gerardo Ramos-Larios, Martín A.  Guerrero
      Abstract: Similar to other classes of astronomical objects, there is a large discrepancy between the total count of theoretically predicted planetary nebulae (PNe) and the number of those actually observed. This discrepancy introduces bias in our attempt to globally understand and characterize the PNe population. Major efforts have been made to find the missing PNe. In particular, the INT Photometric Hα Survey (IPHAS) has, since its debut, provided a whelm of new (candidate) PNe, some of which have been studied in depth using various methodologies such as deep imaging and low- and high-resolution spectroscopy. Here, we present the outcome of the analysis of a first group of these well-investigated IPHAS PNe with a focus on the extended ones. We show that, in general, the missing objects that were expected to be unveiled by the survey (low density, evolved, and distant) are indeed discovered, but the survey also allows the retrieval of “simply” overlooked PNe.
      PubDate: 2022-05-10T00:00:00Z
       
  • Deciphering Solar Magnetic Activity: The Solar Cycle Clock

    • Authors: Robert J. Leamon, Scott W. McIntosh, Alan M. Title
      Abstract: The Sun’s variability is controlled by the progression and interaction of the magnetized systems that form the 22-year magnetic activity cycle (the “Hale Cycle”) as they march from their origin at ∼55° latitude to the equator, over ∼19 years. We will discuss the end point of that progression, dubbed “terminator” events, and our means of diagnosing them. In this paper we expand on the Extended Solar Cycle framework to construct a new solar activity “clock” which maps all solar magnetic activity onto a single normalized epoch based on the terminations of Hale Magnetic Cycles. Defining phase 0*2π on this clock as the Terminators, then solar polar field reversals occur at ∼ 0.2*2π, and the geomagnetically quiet intervals centered around solar minimum start at ∼ 0.6*2π and end at the terminator, thus lasting 40% of the cycle length. At this onset of quiescence, dubbed a “pre-terminator,” the Sun shows a radical reduction in active region complexity and, like the terminator events, is associated with the time when the solar radio flux crosses F10.7 = 90 sfu. We use the terminator-based clock to illustrate a range of phenomena that further emphasize the strong interaction of the global-scale magnetic systems of the Hale Cycle: the vast majority, 96%, of all X-flares happen between the Terminator and pre-Terminator. In addition to the X-rays from violent flares, rapid changes in the number of energetic photons—EUV spectral emission from a hot corona and the F10.7 solar radio flux—impinging on the atmosphere are predictable from the Terminator-normalized unit cycle, which has implications for improving the fidelity of atmospheric modelling.
      PubDate: 2022-05-10T00:00:00Z
       
  • Jovian Planets and Lunar Nodal Cycles in the Earth’s Climate
           Variability

    • Authors: Harald Yndestad
      Abstract: This study utilizes time-series data devised to measure solar irradiation, sea surface temperatures, and temperatures in the lower atmosphere to gain a better understanding of how gravitational effects from the moon and Jovian planets (Jupiter, Saturn, Uranus, and Neptune) influence solar activity and climatic conditions on Earth. Then, standard statistical methods are used to determine the degree of correlation among these time series and construct a Jovian gravitational model. The study reveals a direct relationship between JSUN perihelion coincidences and TSI amplitude variations in cycles up to 4,450 years. The forced solar accumulation of heat in oceans introduces a new phase relation between solar forced cycles and new climate variation. Earth’s axis nutation cycles have coincidences with lunar nodal tide cycles and lunar forced sea surface temperature cycle periods up to 446 years. Earth’s temperature variation shows coincidence with constructive and destructive interference between lunar-forced and accumulated solar-forced temperature variations in oceans. Upcoming events have a computed modern temperature maximum in 2025 and a deep minimum in 2070. Interference between solar-forced temperature cycles of 333,2142, and 4,450 years and a lunar-forced temperature cycle of 445 years indicates that “The Little Ice Age” covers a total period of 820 years from 1330 to 2150 A.D. and an upcoming temporary cold climate period from 2070 to 2150.
      PubDate: 2022-05-10T00:00:00Z
       
  • Planetary Nebulae as Sources of Chemical Enrichment of the Galaxy

    • Authors: Sun Kwok
      Abstract: During the late asymptotic giant branch (AGB) phase of stellar evolution, the element carbon is created through the triple-α nuclear reaction. This is followed by the synthesis of other heavy elements via neutron capture in the core and the dredge-up of these elements to the surface by convection. Simple molecules and solid-state minerals begin to form in the upper photosphere. These molecules and solids are ejected into the interstellar medium by a strong stellar wind. During the subsequent post-AGB evolution, complex organics with aromatic and aliphatic structures are synthesized in the circumstellar envelope. Planetary nebulae, formed by swept-up circumstellar material, are found to show strong spectral signatures of ions, atoms, molecules, and inorganic and organic solids. These ejected materials of planetary nebulae serve as primordial ingredients of formation of new stars and planetary systems. Stellar synthesized organic solids may survive their journeys through the interstellar medium and evidence for remnants of such organics can be found in our own Solar System. In this paper, we summarize the recent observations of circumstellar synthesis of molecules and solids and discuss the implications of these ejected circumstellar materials on the chemical enrichment of the Galaxy and planetary systems.
      PubDate: 2022-05-10T00:00:00Z
       
  • A New Three-Dimensional Empirical Reconstruction Model Using a Stochastic
           Optimization Method

    • Authors: Xun Zhu, Ian J. Cohen, Barry H. Mauk, Romina Nikoukar, Drew L. Turner, Roy B. Torbert
      Abstract: Motivated by MMS mission observations near magnetic reconnection sites, we have developed a new empirical reconstruction (ER) model of the three-dimensional (3D) magnetic field and the associated plasma currents. Our approach combines both the measurements from a constellation of satellites and a set of physics-based equations as physical constraints to build spatially smooth distributions. This ER model directly minimizes the loss function that characterizes the model-measurement differences and the model departures from linear or nonlinear physical constraints using an efficient stochastic optimization method by which the effects of random measurement errors can be effectively included. Depending on the availability of the measured parameters and the adopted physical constraints on the reconstructed fields, the ER model could be either slightly over-determined or under-determined, yielding nearly identical reconstructed fields when solved by the stochastic optimization method. As a result, the ER model remains valid and operational even if the input measurements are incomplete. Two sets of new indices associated respectively with the model-measurement differences and the model departures are introduced to objectively measure the accuracy and quality of the reconstructed fields. While applying the reconstruction model to observations of an electron diffusion region (EDR) observed by NASA’s Magnetospheric Multiscale (MMS) mission, we examine the relative contributions of the errors in the plasma current density arising from random measurement errors and linear approximations made in application of the curlometer technique. It was found that the errors in the plasma current density calculated directly from the measured magnetic fields using a linear approximation were mostly contributed from the nonlinear configuration of the 3D magnetic fields.
      PubDate: 2022-05-09T00:00:00Z
       
  • Ray Tracing of MHD Rossby Waves in the Solar Tachocline: Meridional
           Propagation and Implications for the Solar Magnetic Activity

    • Authors: André S. W. Teruya, Breno Raphaldini, Carlos F. M. Raupp
      Abstract: Rossby waves have been recently recognised for their role in the large-scale spatio-temporal organisation of the solar magnetic activity. Here, we study the propagation of magnetohydrodynamic Rossby waves in a thin layer, representing the solar tachocline. We consider the waves embedded in a meridionally varying background state characterised by a mean zonal flow, which mimics the differential rotation profile of the Sun, and a toroidal magnetic field. Two anti-symmetric toroidal magnetic fields are utilised: one having a global structure with the maximum at around 50o and the other characterised by a narrow band centered at around 20o. We show that for a global structure toroidal magnetic field, the MHD Rossby modes undergo significant meridional propagation, either equatorward or poleward. In addition, the latitude where the waves exhibit a stationary behaviour is sensitive to the strength of the background magnetic field. On the other hand, a narrow band toroidal magnetic field is shown to work as a waveguide for the fast branch of MHD Rossby waves.
      PubDate: 2022-05-05T00:00:00Z
       
  • Measurement of MHD Turbulence Properties by Synchrotron Radiation
           Techniques

    • Authors: Jian-Fu Zhang, Ru-Yue Wang
      Abstract: It is well known that magnetohydrodynamic (MHD) turbulence is ubiquitous in astrophysical environments. The correct understanding of the fundamental properties of MHD turbulence is a pre-requisite for revealing many key astrophysical processes. The development of observation-based measurement techniques has significantly promoted MHD turbulence theory and its implications in astrophysics. After describing the modern understanding of MHD turbulence based on theoretical analysis and direct numerical simulations, we review recent developments related to synchrotron fluctuation techniques. Specifically, we comment on the validation of synchrotron fluctuation techniques and the measurement performance of several properties of magnetic turbulence based on data cubes from MHD turbulence simulations and observations. Furthermore, we propose to strengthen the studies of the magnetization and 3D magnetic field structure’s measurements of interstellar turbulence. At the same time, we also discuss the prospects of new techniques for measuring magnetic field properties and understanding astrophysical processes, using a large number of data cubes from the Low-Frequency Array (LOFAR) and the Square Kilometre Array (SKA).
      PubDate: 2022-05-05T00:00:00Z
       
  • Theory of Fluid Instabilities in Partially Ionized Plasmas: An Overview

    • Authors: Roberto Soler, José Luis Ballester
      Abstract: Partially ionized plasmas (PIP) are essential constituents of many astrophysical environments, including the solar atmosphere, the interstellar medium, molecular clouds, accretion disks, planet ionospheres, cometary tails, etc., where the ionization degree may vary from very weak ionization to almost full ionization. The dynamics of PIP is heavily affected by the interactions between the various charged and neutral species that compose the plasma. It has been shown that partial ionization effects influence the triggering and development of fluid instabilities as, e.g., Kelvin-Helmholtz, Rayleigh-Taylor, thermal, and magneto-rotational instabilities, among others. Here we review the theory of some classic fluid instabilities that are present in PIP and highlight the unique effects introduced by partial ionization. The main emphasis of the review is put on instabilities in the partially ionized solar atmospheric plasma, although other astrophysical applications are also mentioned. We focus on the mathematical and theoretical investigation of the onset and exponential growth of the instabilities. Results of the nonlinear evolution obtained from full numerical simulations are also discussed.
      PubDate: 2022-05-05T00:00:00Z
       
  • Geomagnetic Response to Rapid Increases in Solar Wind Dynamic Pressure:
           Event Detection and Large Scale Response

    • Authors: Michael Madelaire, Karl M. Laundal, Jone P. Reistad, Spencer M. Hatch, Anders Ohma, Stein Haaland
      Abstract: Discontinuities in the solar wind trigger a variety of processes in the magnetosphere-ionosphere system. A rapid increase in solar wind dynamic pressure causes compression of the magnetosphere. This manifests itself as a positive perturbation of the horizontal ground magnetic field at low/mid latitudes. In this study we present a method for detecting these discontinuities in situ solar wind data by using the random forest machine learning algorithm. Each detected event is propagated to Earth and its arrival time is aligned with a corresponding response in the low latitude ground magnetic field. A list of 3,867 events, detected between 1994 and 2019, is presented. We use the list in a superposed epoch analysis of the low/mid latitude response in the ground magnetic field at different local times, and of the high latitude response using the Polar Cap index. A dawn-dusk asymmetry is found at low/mid latitudes with weaker positive perturbations at dawn compared to any other local time sector. This suggests a stronger ring current contribution at dawn assuming the magnetopause contribution to be uniform. During northward IMF the initial response is asymmetric, but returns to symmetry after 30 min. During southward IMF the low/mid latitude response decays rapidly in all local sectors except dawn. After around 30 min the asymmetry has flipped such that the strongest positive perturbation is at dawn. This suggests an amplification of the partial ring current. In addition, a noon-midnight asymmetry is observed during southward IMF with the strongest positive perturbation on the night side suggesting a significant contribution from dipolarization of the geomagnetic field in the near tail. The complex geomagnetic response to rapid increases in solar wind dynamic pressure demonstrates a need for further statistical analyses. Event lists, such as the one presented here, are critical components in such studies.
      PubDate: 2022-05-05T00:00:00Z
       
  • The Transmission of ULF Waves From the Solar Wind to the Magnetosphere: An
           Analysis of Some Critical Aspects

    • Authors: U. Villante, D. Recchiuti, S. Di Matteo
      Abstract: Several critical aspects may influence the analysis of the relationship between the solar wind (SW) and magnetospheric fluctuations, for example, the characteristics and frequency of SW fluctuations that are expected to impinge the magnetosphere may not be the same when they are observed by spacecraft located at different places in front of the magnetosphere; similarly, the choice of analytical methods adopted for the spectral analysis might influence the frequency estimate (as well as the wave identification itself) both in the SW and magnetosphere. Focusing our attention on these aspects, we present an analysis of SW compressional fluctuations (f ≈ 1–5 mHz), following two interplanetary shocks observed by two interplanetary spacecraft, regarded as two different situations in terms of spacecraft separation and distance from the magnetosphere. Our results show that some differences in the characteristics of SW fluctuations emerge when the same stream is observed at different places and confirm the critical role of analytical methods in determining fluctuation characteristics. We compared aspects of SW fluctuations with those of magnetospheric fluctuations following the sudden impulses due to the impact of interplanetary shocks. For this scope, we examined observations by two satellites at geostationary orbit and at several ground-based stations. We found that the magnetospheric fluctuations were related to compressional SW fluctuations approximately at the same frequencies, with no evidence for wave activity of internal origin or directly driven by the shock impact.
      PubDate: 2022-05-03T00:00:00Z
       
  • Multi-Variate LSTM Prediction of Alaska Magnetometer Chain Utilizing a
           Coupled Model Approach

    • Authors: Matthew Blandin, Hyunju K. Connor, Doğacan S. Öztürk, Amy M. Keesee, Victor Pinto, Md Shaad Mahmud, Chigomezyo Ngwira, Shishir Priyadarshi
      Abstract: During periods of rapidly changing geomagnetic conditions electric fields form within the Earth’s surface and induce currents known as geomagnetically induced currents (GICs), which interact with unprotected electrical systems our society relies on. In this study, we train multi-variate Long-Short Term Memory neural networks to predict magnitude of north-south component of the geomagnetic field ( BN ) at multiple ground magnetometer stations across Alaska provided by the SuperMAG database with a future goal of predicting geomagnetic field disturbances. Each neural network is driven by solar wind and interplanetary magnetic field inputs from the NASA OMNI database spanning from 2000–2015 and is fine tuned for each station to maximize the effectiveness in predicting BN . The neural networks are then compared against multivariate linear regression models driven with the same inputs at each station using Heidke skill scores with thresholds at the 50, 75, 85, and 99 percentiles for BN . The neural network models show significant increases over the linear regression models for BN thresholds. We also calculate the Heidke skill scores for d BN /dt by deriving d BN /dt from BN predictions. However, neural network models do not show clear outperformance compared to the linear regression models. To retain the sign information and thus predict BN instead of BN , a secondary so-called polarity model is utilized. The polarity model is run in tandem with the neural networks predicting geomagnetic field in a coupled model approach and results in a high correlation between predicted and observed values for all stations. We find this model a promising starting point for a machine learned geomagnetic field model to be expanded upon through increased output time history and fast turnaround times.
      PubDate: 2022-05-02T00:00:00Z
       
  • Statistical Analysis of Bifurcating Region 2 Field-Aligned Currents Using
           AMPERE

    • Authors: H. K. Sangha , S. E. Milan , B. J. Anderson , H. Korth 
      Abstract: We present a statistical analysis of the occurrence of bifurcations of the Region 2 (R2) Field-Aligned Current (FAC) region, observed by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). Previously, these have been shown to occur as the polar cap contracts after substorm onset, the beginning of the growth phase. During this phase both the Region 1 (R1) and R2 currents move equatorwards as the polar cap expands. Following onset, the R1 FAC region contracts polewards but the R2 FAC continues to expand equatorwards before eventually fading. At the same time, a new R2 FAC develops equatorwards of the R1 FAC. We have proposed that the bifurcated FACs formed during substorms are associated with plasma injections from the magnetotail into the inner magnetosphere, and that they might be the FAC signature associated with Sub-Auroral Polarization Streams (SAPS). We investigate the seasonal dependence of the occurrence of bifurcations from 2010 to 2016, determining whether they occur predominantly at dawn or dusk. Region 2 Bifurcations (R2Bs) are observed most frequently in the summer hemisphere and at dusk, and we discuss the possible influence of ionospheric conductance. We also discuss a newly discovered UT dependence of the R2B occurrences between 2011 and 2014. This dependence is characterized by broad peaks in occurrence near 09 and 21 UT in both hemispheres. Reasons for such a preference in occurrence are explored.
      PubDate: 2022-05-02T00:00:00Z
       
 
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