Subjects -> ASTRONOMY (Total: 94 journals)
Showing 1 - 46 of 46 Journals sorted alphabetically
Advances in Astronomy     Open Access   (Followers: 49)
Annual Review of Astronomy and Astrophysics     Full-text available via subscription   (Followers: 50)
Annual Review of Earth and Planetary Sciences     Full-text available via subscription   (Followers: 67)
Artificial Satellites     Open Access   (Followers: 21)
Astrobiology     Hybrid Journal   (Followers: 11)
Astronomical & Astrophysical Transactions: The Journal of the Eurasian Astronomical Society     Hybrid Journal   (Followers: 7)
Astronomical Review     Open Access   (Followers: 5)
Astronomische Nachrichten     Hybrid Journal   (Followers: 4)
Astronomy & Geophysics     Hybrid Journal   (Followers: 49)
Astronomy and Astrophysics     Full-text available via subscription   (Followers: 67)
Astronomy and Computing     Hybrid Journal   (Followers: 6)
Astronomy Letters     Hybrid Journal   (Followers: 22)
Astronomy Reports     Hybrid Journal   (Followers: 22)
Astronomy Studies Development     Open Access   (Followers: 15)
Astroparticle Physics     Hybrid Journal   (Followers: 10)
Astrophysical Bulletin     Hybrid Journal   (Followers: 4)
Astrophysics     Hybrid Journal   (Followers: 35)
Astrophysics and Space Science     Hybrid Journal   (Followers: 49)
Astrophysics and Space Sciences Transactions (ASTRA)     Open Access   (Followers: 60)
Astropolitics: The International Journal of Space Politics & Policy     Hybrid Journal   (Followers: 13)
Celestial Mechanics and Dynamical Astronomy     Hybrid Journal   (Followers: 15)
Chinese Astronomy and Astrophysics     Full-text available via subscription   (Followers: 25)
Colloid Journal     Hybrid Journal   (Followers: 2)
Comptes Rendus : Physique     Open Access   (Followers: 2)
Computational Astrophysics and Cosmology     Open Access   (Followers: 6)
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 143)
Earth, Moon, and Planets     Hybrid Journal   (Followers: 47)
Earth, Planets and Space     Open Access   (Followers: 77)
EAS Publications Series     Full-text available via subscription   (Followers: 8)
EPL Europhysics Letters     Partially Free   (Followers: 8)
Experimental Astronomy     Hybrid Journal   (Followers: 38)
Expert Opinion on Astronomy and Astrophysics     Open Access   (Followers: 8)
Extreme Life, Biospeology & Astrobiology - International Journal of the Bioflux Society     Full-text available via subscription   (Followers: 4)
Few-Body Systems     Hybrid Journal   (Followers: 1)
Foundations of Physics     Hybrid Journal   (Followers: 40)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 15)
Galaxies     Open Access   (Followers: 6)
Globe, The     Full-text available via subscription   (Followers: 3)
Gravitation and Cosmology     Hybrid Journal   (Followers: 6)
Icarus     Hybrid Journal   (Followers: 71)
International Journal of Advanced Astronomy     Open Access   (Followers: 21)
International Journal of Astrobiology     Hybrid Journal   (Followers: 4)
International Journal of Astronomy     Open Access   (Followers: 22)
International Journal of Astronomy and Astrophysics     Open Access   (Followers: 36)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 15)
International Letters of Chemistry, Physics and Astronomy     Open Access   (Followers: 8)
ISRN Astronomy and Astrophysics     Open Access   (Followers: 14)
Journal for the History of Astronomy     Full-text available via subscription   (Followers: 20)
Journal of Astrobiology & Outreach     Open Access   (Followers: 5)
Journal of Astronomical Instrumentation     Open Access   (Followers: 3)
Journal of Astrophysics     Open Access   (Followers: 33)
Journal of Astrophysics and Astronomy     Open Access   (Followers: 58)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 133)
Journal of Geophysical Research : Planets     Full-text available via subscription   (Followers: 116)
Journal of Geophysical Research : Space Physics     Full-text available via subscription   (Followers: 136)
Journal of High Energy Astrophysics     Full-text available via subscription   (Followers: 25)
Kinematics and Physics of Celestial Bodies     Hybrid Journal   (Followers: 11)
KronoScope     Hybrid Journal   (Followers: 1)
Macalester Journal of Physics and Astronomy     Open Access   (Followers: 5)
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 13)
Monthly Notices of the Royal Astronomical Society : Letters     Hybrid Journal   (Followers: 2)
Nature Astronomy     Hybrid Journal   (Followers: 14)
New Astronomy     Hybrid Journal   (Followers: 26)
New Astronomy Reviews     Full-text available via subscription   (Followers: 19)
Nonlinear Dynamics     Hybrid Journal   (Followers: 19)
NRIAG Journal of Astronomy and Geophysics     Open Access   (Followers: 4)
Physics of the Dark Universe     Open Access   (Followers: 4)
Planetary and Space Science     Hybrid Journal   (Followers: 106)
Planetary Science     Open Access   (Followers: 52)
Proceedings of the International Astronomical Union     Full-text available via subscription   (Followers: 2)
Publications of the Astronomical Society of Australia     Hybrid Journal   (Followers: 3)
Publications of the Astronomical Society of Japan     Hybrid Journal   (Followers: 4)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 20)
Research in Astronomy and Astrophysics     Full-text available via subscription   (Followers: 38)
Revista Mexicana de Astronomía y Astrofísica     Open Access   (Followers: 3)
Science China : Physics, Mechanics & Astronomy     Full-text available via subscription   (Followers: 4)
Science China Physics, Mechanics & Astronomy     Hybrid Journal   (Followers: 4)
Solar Physics     Hybrid Journal   (Followers: 29)
Solar System Research     Hybrid Journal   (Followers: 15)
Space Science International     Open Access   (Followers: 118)
Space Science Reviews     Hybrid Journal   (Followers: 92)
Space Weather     Full-text available via subscription   (Followers: 27)
Transport and Aerospace Engineering     Open Access   (Followers: 13)
Universe     Open Access   (Followers: 6)
Similar Journals
Journal Cover
Earth, Moon, and Planets
Journal Prestige (SJR): 0.63
Citation Impact (citeScore): 1
Number of Followers: 47  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1573-0794 - ISSN (Online) 0167-9295
Published by Springer-Verlag Homepage  [2469 journals]
  • Statistical Thermodynamics of Surface-Bounded Exospheres

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      Abstract: Abstract Neutral exospheres of large airless bodies consist of atoms or molecules on ballistic trajectories. An import example is the lunar water exosphere, thought to transport water to cold traps. In anticipation of future observational measurements, the theory of thermalized surface-bounded gravitationally-bound exospheres is further developed. The vertical density profile is calculated using thermodynamic averages of an ensemble of ballistic trajectories. When the launch velocities follow the Maxwell–Boltzmann Flux distribution, the classical density profile results. For many other probability distributions, including thermal desorption from a vertical wall, the density diverges logarithmically near the surface. Hence, an exosphere resulting from thermal desorption from a rough surface includes a ground-hugging population that appears to be colder than the surface. Another insight derived from the thermodynamic perspective is that cold traps can be interpreted in terms of the frostpoint of the water exosphere, if the long-term average of the pressure of the exosphere is considered. Ice in lunar caves is long-lasting only if the cave interior is below the cold trap temperature threshold.
      PubDate: 2022-05-12
       
  • Identifying Shocked Feldspar on Mars Using Perseverance Spectroscopic
           Instruments: Implications for Geochronology Studies on Returned Samples

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      Abstract: Abstract The Perseverance rover (Mars 2020) mission, the first step in NASA’s Mars Sample Return (MSR) program, will select samples for caching based on their potential to improve understanding Mars’ astrobiological, geological, geochemical, and climatic evolution. Geochronologic analyses will be among the key measurements planned for returned samples. Assessing a sample’s shock history will be critical because shock metamorphism could influence apparent sample age. Shock effects in one Mars-relevant mineral class, plagioclase feldspar, have been well-documented using various spectroscopy techniques (thermal infrared reflectance, emission, and transmission spectroscopy, Raman, and luminescence). A subset of these data will be obtained with the SuperCam and SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) instruments onboard Perseverance to inform caching decisions for MSR. Here, we review shock indicators in plagioclase feldspar as revealed in Raman, luminescence, and IR spectroscopy lab data, with an emphasis on Raman spectroscopy. We consider how this information may inform caching decisions for selecting optimal samples for geochronology measurements. We then identify challenges and make recommendations for both in situ measurements performed with SuperCam and SHERLOC and for supporting lab studies to enhance the success of geochronologic analyses after return to Earth.
      PubDate: 2022-05-03
       
  • The Distribution of Craters Within Craters

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      Abstract: Abstract The interior of a crater should have a lower mean areal density of smaller impact craters than nearby plains have, because the impacts are spread out over a larger surface area, and because the crater’s wall partially shields its interior. Inside a crater shaped like a spherical bowl (a spherical cap turned upside-down), smaller primary impact craters should be spread uniformly, but secondary craters have a more complicated distribution, usually concentrated near the center. These results may help to distinguish between populations of primary and secondary craters, and should be of interest for interpreting counts of craters within craters.
      PubDate: 2022-03-23
       
  • Photometric Correction of Images of Visible and Near-Infrared Bands from
           Chandrayaan-1 Hyper-Spectral Imager (HySI)

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      Abstract: Abstract Photometric correction is a necessary step in planetary image pre-processing since the images of planetary surfaces are acquired by orbiting spacecraft at various observational geometries. In this study, visible (748 nm) and near-infrared (948 nm) bands of Hyper Spectral Imager (HySI) onboard Chandrayaan-1 have been used to derive a preliminary photometric correction for lunar data. The purpose of the proposed photometric correction for HySI is to convert observations taken at solar incidence (i), sensor emission (e), and the solar phase angles (α) to a fixed geometry by applying i = α = 30° and e = 0° to each image. The Lommel–Seeliger function was used to model the lunar limb darkening effect, while topography data from the merged Digital Elevation Model of Lunar Reconnaissance Orbiter—Lunar Orbiter Laser Altimeter (LRO-LOLA) and SELENE Terrain Camera (TC) was used to correct local topographic effects. Data from Moon Mineralogy Mapper (M3), SELENE Multiband Imager (MI) and Clementine Ultraviolet and Visible Camera (UV/VIS) were also used to compare radiance, reflectance and phase functions derived from HySI. Our analysis reveals that HySI is darker than M3 primarily due to low surface radiance conditions observed by HySI. The derived phase functions for the two HySI bands indicate a good correlation between the derived reflectance and phase angle as well as with the phase functions derived for the empirically corrected M3 data. This approach led to the derivation of a photometric correction for maria regions. Finally, it is expected that the proposed correction would be applicable to all HySI images covering the lunar mare region.
      PubDate: 2021-12-06
      DOI: 10.1007/s11038-021-09544-0
       
  • Instability of Triangular Equilibrium Points in the Restricted Three-Body
           Problem Under Effects of Circumbinary Disc, Radiation Pressure and P–R
           Drag

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      Abstract: Abstract The paper examines instability of triangular equilibrium points of a test particle in the gravitational field of two primaries radiating with effective Poynting–Robertson (P–R) drag, enclosed by circumbinary disc. The equations of motion are derived and positions of triangular equilibrium points are located. It is seen that the locations are affected by the disc, radiation pressure and P–R drag of the primaries. In particular, for our numerical computations of the locations of the triangular equilibrium points and the linear stability analysis, we consider a low-mass pulsating star, IRAS 11472-0800 as the bigger primary, with a young white dwarf star; G29-38 as the smaller primary. We observe that the disc does not change the x-coordinates of the triangular points while their y-coordinates are been altered. However, radiation pressure, P–R drag and the mass parameter µ mainly contribute in shifting the location of the triangular points. As regards the stability analysis, these points are in general unstable under the combine effects of radiation, P–R drag and disc, in the entire range of the mass parameter due to complex roots with positive real parts. Further, in order to discern the effects of the parameters on the instability outcome, we broaden the range of the mass parameter to accommodate small values of the mass parameters. We observe that in the absence of radiation and the presence of disc, when the mass parameter is less than the critical mass, all the roots are pure imaginary and the triangular point is stable. However, when \(\mu = 0.038521\) , the four roots are complex, but turn pure imaginary quantities when the disc is present. This proves that the disc is a stabilizing force while the radiation pressure and P–R drag induces instability around the triangular equilibrium points in the entire range of the mass parameter due to the presence of complex roots with positive real parts.
      PubDate: 2021-10-21
      DOI: 10.1007/s11038-021-09543-1
       
  • Migration of Water Molecules in the Permanently Shaded Areas of Polar
           Areas of Mercury

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      Abstract: Abstract Radar observations of the surface of Mercury had revealed areas with bright reflective properties in both polar regions of the planet. It was suggested that such areas contain depositions of volatile compounds, including water. In this paper, we investigated migration of water molecules to the permanently shaded areas, located in the impact crater in the polar regions of Mercury. To simulate the migration of water molecules in the exosphere of Mercury, we used the Monte Carlo method. To estimate the proportion of water molecules falling into cold traps in the polar regions of Mercury, we estimated the area of such regions. We found that the area of permanently shaded areas near the north pole of the planet reaches 23,300 km2, and in the area of the south pole—45,500 km2. Most of the water molecules (~ 92%) will be destroyed as a result of photolysis, and ~ 7.5% of them will be destroyed while they are on the planet's surface between hops. The fraction of water molecules that left the planet's exosphere as a result of reaching the escape velocity is only 0.3%. The fraction of water molecules trapped in permanently shaded areas in the polar regions of Mercury reaches 7.8% of the total number of particles participating in the simulation. Only 2.2% of them can be trapped in cold traps in the North Pole region and 5.6% in the South Pole region.
      PubDate: 2021-08-28
      DOI: 10.1007/s11038-021-09542-2
       
  • Test of the Hypothesis for an Unknown Distant Massive Planet in the Solar
           

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      Abstract: Abstract This article presents the results of an analysis of Tisserand’s constant for 1389 long-period comets in relation to a hypothetical planet. A mechanism is proposed to apply Tisserand’s criterion for a relatively trans-Neptunian planet with a notable inclination and orbit eccentricity. In particular, the algorithm considers the planet’s heliocentric distance in the era of a clearly-defined transformational change in the cometary orbit. Thus, we carried out the corresponding calculations by simulating the planet motion plane. This study allows a comparative analysis of Tisserand constant values for proposed hypothetical planet parameters. The most notable result is for a planet at a proposed distance of 340 AU.
      PubDate: 2021-07-25
      DOI: 10.1007/s11038-021-09541-3
       
  • The EURONEAR Lightcurve Survey of Near Earth Asteroids—Teide
           Observatory, Tenerife, 2015

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      Abstract: Abstract One meter class telescopes could bring important contributions in the acquisition of lightcurves of near earth asteroids (NEAs), based on which rotations and other physical properties could be derived or constrained. Part of a collaboration between IAC, ESA and the EURONEAR during the semester 2015A, the IAC80 and OGS telescopes at Teide Observatory in Tenerife were allocated for a photometric project during 64 nights spread in a few observing runs. The main funding for this long observing mission was raised by the student observer Radu Cornea from private sponsors based in his natal city of Sibiu, Romania, mentioned in the Acknowledgements. We observed 33 lightcurves of NEAs not published before, including 10 potentially hazardous asteroids (PHAs). Based on the quality of the Fourier period fits, we sorted the results in four groups which include 7 secured periods, 9 candidate periods, 10 tentative periods and 7 objects not solved. We resolved periods or suggested constraints for 13 NEAs having no other rotation knowledge (including 3 PHAs), confirming periods for other 6 targets published by other authors (mainly by Brian Warner). We suggested tumbling or binary nature for 6 targets (probing one of them) recommended for future dedicated campaigns. We derived ellipsoid shape ratios for 21 NEAs (including 4 PHAs) not known before.
      PubDate: 2021-04-26
      DOI: 10.1007/s11038-021-09540-4
       
  • The Mechanical Properties of Chelyabinsk LL5 Chondrite Under Compression
           and Tension

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      Abstract: Abstract The mechanical properties of Chelyabinsk LL5 chondrite (Chelyabinsk meteorite) were studied by uniaxial compression and diametral compression/indirect tension test. Twenty cylindrical samples, 10 for compression and 10 for tension, with the diameter 3.3 mm and 1.65 mm in height have been prepared for testing. It was shown that the strength of the tested samples under compression almost 45 times greater than it is at tension: 372 ± 10 MPa and 8.2 ± 0.7 MPa, respectively. Fracture behaviour under compression and tension was similar and can be characterised as brittle. The obtained compression strength of the Chelyabinsk meteorite lies close to the maximal values of strength for many other chondrites, whereas its tensile strength magnitude resides in the bottom quarter of the range of similar measurements. It may be caused by the small sizes of the investigated samples together with a large number of tiny cracks between the grains in the Chelyabinsk chondrite. Our estimations have shown that if one assumes that the initial shape of the Chelyabinsk fireball was spherical or ellipsoidal, then its fragmentation stress is close to the experimental tensile strength and much lower than the compression strength. Hence, a stress state equivalent to one appearing at the indirect tension test could occur in the Chelyabinsk fireball during its fall in the Earth atmosphere.
      PubDate: 2021-02-27
      DOI: 10.1007/s11038-021-09539-x
       
  • Depths of Copernican Craters on Lunar Maria and Highlands

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      Abstract: Abstract We present a study on the relationship between the ratio of the depth of a crater to its diameter and the diameter for lunar craters both on the maria and on the highlands. We consider craters younger than 1.1 billion years in age, i.e. of Copernican period. The aim of this work is to improve our understanding of such relationships based on our new estimates of the craters’s depth and diameter. Previous studies considered similar relationships for much older craters (up to 3.2 billion years). We calculated the depths of craters with diameters from 10 to 100 km based on the altitude profiles derived from data obtained by the Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter (LRO). The obtained ratios h/D of the depths h of the craters to their diameters D can differ by up to a factor of two for craters with almost the same values of diameters. The linear and power approximations (regressions) of the dependence of h/D on D were made for simple and complex Copernican craters selected from the data from Mazrouei et al. (Science 363:253–255, 2019) and Losiak et al. (Lunar Impact Crater Database, 2015). For the separation of highland craters into two groups based only on their dependences of h/D on D, at D < 18 km these are mostly simple craters, although some complex craters can have diameters D ≥ 16 km. Depths of mare craters with D ≤ 14 km are greater than 0.15D. Following Pike’s (Lunar Planet Sci XII:845–847, 1981) classification, we group mare craters of D < 15 km as simple craters. Mare craters with 15 < D < 18 km fit both approximation curves for simple and complex craters. Depths of mare craters with D > 18 km are in a better agreement with the approximation curve of h/D versus D for complex craters than for simple craters. At the same diameter, mare craters are deeper than highland craters at a diameter smaller than 30–40 km. For greater diameters, highland craters are deeper. The values of h/D for our approximation curves are mainly smaller than the values of the curve by Pike (in: Roddy, Pepin, Merrill (eds) Impact and explosion cratering: planetary and terrestrial implications, University of Arizona Press, Tucson, 1977) at D < 15 km. Only for mare craters at D < 11 km, our approximation curve is a little higher than the curve by Pike (1977). For our power approximations, the values of h/D obtained for complex craters are greater than those obtained by Pike (1981) at D > 53 km for highland craters, and at D < 80 km for mare craters.
      PubDate: 2021-01-29
      DOI: 10.1007/s11038-021-09538-y
       
  • Revisiting Lunar Seismic Experiment Data Using the Multichannel Simulation
           with One Receiver (MSOR) Approach and Random Field Modeling

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      Abstract: Abstract Major advancements in surface wave testing over the past 2 decades have led researchers to revisit and re-analyze archived seismic records, particularly those involving measurements on the Moon. The goal of such recent efforts with lunar seismic measurements has been to gain further insights into lunar geology. We examined the active seismic data from the Apollo 16 mission for their surface wave information using a multichannel approach. The inversion of Rayleigh surface waves provided a subsurface estimate for the uppermost 8 m of the lunar subsurface with the shear wave velocities varying from 40 to 50 m/s at the surface to velocities in the range of 95–145 m/s with an average of 120 m/s at a depth of about 7 m. Generally, the results from this inversion demonstrated good agreement with previous studies. Also, we carried out numerical modeling of wave propagation in a highly-heterogeneous domain to examine the effects of such anomalous features on the acquired seismograms. Results confirmed that a sharp-contrast bi-material domain can indeed produce significant coda wave as reflected on the lunar seismic traces.
      PubDate: 2020-12-01
      DOI: 10.1007/s11038-020-09536-6
       
  • Automated Extraction of Crater Rims on 3D Meshes Combining Artificial
           Neural Network and Discrete Curvature Labeling

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      Abstract: Abstract One of the challenges of planetary science is the age determination of geological units on the surface of the different planetary bodies in the solar system. This serves to establish a chronology of the geological events occurring on these different bodies, hence to understand their formation and evolution processes. An approach for dating planetary surfaces relies on the analysis of the impact crater densities with size. Approaches have been proposed to automatically detect impact craters in order to facilitate the dating process. They rely on color values from images or elevation values from Digital Elevation Models (DEM). In this article, we propose a new approach for crater detection, more specifically using their rims. The craters can be characterized by a round shape that can be used as a feature. The developed method is based on an analysis of the DEM geometry, represented as a 3D mesh, followed by curvature analysis. The classification process is done with one layer perceptron. The validation of the method is performed on DEMs of Mars, acquired by a laser altimeter aboard NASA’s Mars Global Surveyor spacecraft and combined with a database of manually identified craters. The results show that the proposed approach significantly reduces the number of false negatives compared to others based on topographic information only.
      PubDate: 2020-12-01
      DOI: 10.1007/s11038-020-09535-7
       
  • RETRACTED ARTICLE: Aspect Sensitivity Considerations in Interpreting Radar
           Meteor Range-Spread Trail Echo Durations

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      PubDate: 2020-08-01
      DOI: 10.1007/s11038-007-9211-1
       
  • Editorial

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      PubDate: 2020-07-01
      DOI: 10.1007/s11038-020-09531-x
       
  • Study of Coronal Mass Ejections Succeeding the Associated X-Ray and
           γ-Ray Burst Solar Flares

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      Abstract: Abstract This study is dedicated to the investigation of the characteristics of CMEs following the associated X-ray and γ-ray burst solar flares. Investigated 14786 CME events and 5092 Gamma Burst Monitor (GBM) solar flare events recorded during the solar period 2008–2017, found 503 (about 10%) CME events associated with GBM post-flare events (hereafter, GBM post-flare—CME). All of these 503 events (100%) are associated with solar flares detected simultaneously in both GBM and RHESI (γ -ray solar flare possibly associated with X-ray). The associated CMEs with GBM post-flare events are wider than non-associated CME events. These results indicate that, as the flare’s flux increases, the width of the associated CME increases. The Gamma burst solar flares accelerate CMEs, but with less extent than do non-associated or associated with X-ray solar flare only events. The GBM post-flare—CME associated events have a mean speed near the solar wind average speed approximately (which is less than speed of CMEs associated with X-ray solar flares only) and faster than non-associated events. The dominant CME initial speed of the GBM post-flare—CME associated events is ~ 300 (Km/s). The CME mean mass of the GBM post-flare—CME associated events indicate that the CMEs occurred after the solar flare is on average more massive than other CMEs. Found the relationship between the mass of the GBM post-flare—CME associated events and the CME width to be on the form: (CME Mass) = − 8.6 × 10+14 + 2.9 × 10+13 × (CME width).
      PubDate: 2020-07-01
      DOI: 10.1007/s11038-020-09534-8
       
  • Exposure Ages, Noble Gases and Nitrogen in the Ordinary Chondrite Karimati
           (L5)

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      Abstract: Abstract Noble gas and nitrogen isotopic compositions of Karimati ordinary (L5) chondrite are presented. Aliquots of the meteorite were studied in two noble gas mass spectrometers. Its cosmic ray exposure (CRE) history, trapped noble gases and nitrogen isotopic systematic are examined. The compositions of Ne and Kr in this meteorite indicate presence of mixture of solar wind and Q trapped components. In addition to the primordial components, radiogenic 129Xe (from the decay of short-lived radioactive 129I) is observed in the two aliquots (129Xe/132Xe ranges between 1.054 and 1.311). The U/Th-4He and K-40Ar ages are discordant. U/Th-4He ages are younger than the K-40Ar ages, indicating loss of helium. The trapped N component is isotopically light analogous to Q gas/solar wind. The cosmic-ray exposure ages of the two aliquots are 16.1 ± 2.7 Ma and 16.6 ± 2.0 Ma based on the cosmogenic 21Nec and 38Arc concentrations.
      PubDate: 2020-07-01
      DOI: 10.1007/s11038-020-09532-w
       
  • The Subjectivity in Identification of Martian Channel Networks and Its
           Implication for Citizen Science Projects

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      Abstract: Abstract The Martian surface is incised by numerous valley networks, which indicate the planet experienced sustained widespread flowing water in the past (e.g. Carr in Water on Mars, Oxford University Press, New York, 1996; Phil Trans R Soc A 370:2193–2212, 2012. https://doi.org/10.1098/rsta.2011.0500). Examining the distribution and geometries of these valley networks provides invaluable information about the Martian climate during the period of formation. The recent advancement in high resolution images has provided an opportunity to build upon past valley maps of Mars (Bahia et al. in LPSC 2018, 2018), however, the identification of these valley networks is extremely time-consuming. A citizen science project may aid in reducing this time-consuming process; this project conducts a valley mapping task with participants of varying expertise in valley mapping to determine whether a citizen science project of this kind should be worth pursuing. This was conducted in a region adjacent to Vogel Crater (36.1° S, 10.2° W). Repeated mapping of the area (a repeatability test) found that participants with low experience in valley mapping (22 a-level physics student’s representative of the public) were inconsistent when mapping valleys. Additionally, when comparing the results of participants within this group (a reproducibility test), the majority of reproduced valleys are false positives (i.e. incorrectly traced valleys). These results were consistent with those found for the medium experience group (45 2nd year geology undergraduates). The validated tracings of the low experience group improve upon the number and total length of valleys mapped by previous studies (Hynek et al. in J Geophys Res 115:1–14, 2010). To validate these valleys requires the input of an expert to remove false positives which is less time consuming than manually mapping the images; this may indicate that a citizen science project is worth pursuing. However, to effectively identify the maximum amount of valleys an expert is required.
      PubDate: 2020-07-01
      DOI: 10.1007/s11038-020-09530-y
       
  • Statistical Characteristics on SEPs, Radio-Loud CMEs, Low Frequency Type
           

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      Abstract: Abstract We have statistically analyzed a set of 115 low frequency (Deca-Hectometer wavelengths range) type II and type III bursts associated with major Solar Energetic Particle (SEP: Ep > 10 MeV) events and their solar causes such as solar flares and coronal mass ejections (CMEs) observed from 1997 to 2014. We classified them into two sets of events based on the duration of the associated solar flares:75 impulsive flares (duration < 60 min) and 40 gradual flares (duration > 60 min).On an average, the peak flux (integrated flux) of impulsive flares × 2.9 (0.32 J m−2) is stronger than that of gradual flares M6.8 (0.24 J m−2). We found that impulsive flare-associated CMEs are highly decelerated with larger initial acceleration and they achieved their peak speed at lower heights (− 27.66 m s−2 and 14.23 Ro) than the gradual flare-associated CMEs (6.26 m s−2 and 15.30 Ro), even though both sets of events have similar sky-plane speed (space speed) within LASCO field of view. The impulsive flare-associated SEP events (Rt = 989.23 min: 2.86 days) are short lived and they quickly reach their peak intensity (shorter rise time) when compared with gradual flares associated events (Rt = 1275.45 min: 3.34 days). We found a good correlation between the logarithmic peak intensity of all SEPs and properties of CMEs (space speed: cc = 0.52, SEcc = 0.083), and solar flares (log integrated flux: cc = 0.44, SEcc = 0.083). This particular result gives no clear cut distinction between flare-related and CME-related SEP events for this set of major SEP events. We derived the peak intensity, integrated intensity, duration and slope of these bursts from the radio dynamic spectra observed by Wind/WAVES. Most of the properties (peak intensity, integrated intensity and starting frequency) of DH type II bursts associated with impulsive and gradual flare events are found to be similar in magnitudes. Interestingly, we found that impulsive flare-associated DH type III bursts are longer, stronger and faster (31.30 min, 6.43 sfu and 22.49 MHz h−1) than the gradual flare- associated DH type III bursts (25.08 min, 5.85 sfu and 17.84 MHz h−1). In addition, we also found a significant correlation between the properties of SEPs and key parameters of DH type III bursts. This result shows a closer association of peak intensity of the SEPs with the properties of DH type III radio bursts than with the properties DH type II radio bursts, atleast for this set of 115 major SEP events.
      PubDate: 2020-07-01
      DOI: 10.1007/s11038-020-09533-9
       
  • Dark Matter Objects: Possible New Source of Gravitational Waves

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      Abstract: Abstract Gravitational waves from mergers of black holes and neutron stars are now being detected by LIGO. Here we look at a new source of gravitational waves, i.e., a class of dark matter objects whose properties were earlier elaborated. We show that the frequency of gravitational waves and strains on the detectors from such objects (including their mergers) could be within the sensitivity range of LIGO. The gravitational waves from the possible mergers of these dark matter objects will be different from those produced by neutron star mergers in the sense that they will not be accompanied by electromagnetic radiation since dark matter does not couple with radiation.
      PubDate: 2019-10-01
      DOI: 10.1007/s11038-019-09527-2
       
  • Superfast Exoplanets and 9600 s

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      Abstract: Abstract Motion of a substantial part of the superfast exoplanets is found to be in the close resonance with the well-known “solar” timescale \(P_{0} \approx 0.11\) days and/or the timescale 2 \(P_0\) / \(\pi \approx 0.07\) days (at 99.9% confidence for exoplanet periods \(P < 2\) days). There is also a noticeable lack of the exoplanetary “unstable” orbits with \(P \approx 3 \pi\) \(P_0\) \(\,\approx 1.05\) days, which copies the famous “period gap” of the cataclysmic variables at \(P \approx 0.11\) days; strangely enough, the ratio of the central periods of these two gaps is equal to \(\pi ^2\) . The exoplanet phenomenon is supposed to be caused by a coherent, with the \(P_0\)  timescale, oscillation of gravity, operating within the extra-solar planetary systems.
      PubDate: 2019-10-01
      DOI: 10.1007/s11038-019-09526-3
       
 
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