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  • Articles  (23)
  • 2015-2019  (23)
  • 2015  (23)
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  • Articles  (23)
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  • 2015-2019  (23)
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  • 1
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    Santa Lucia (2008) (L6) Chondrite, a Recent Fall: Composition, Noble Gases, Nitrogen and Cosmic Ray Exposure Age (2015)
    Springer
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    Publication Date: 2015-11-29
    Description: The Santa Lucia (2008)—one the most recent Argentine meteorite fall, fell in San Juan province, Argentina, on 23 January 2008. Several masses (total ~6 kg) were recovered. Most are totally covered by fusion crust. The exposed interior is of light-grey colour. Chemical data [olivine (Fa 24.4 ) and low-Ca pyroxene (En 77.8 Fs 20.7 Wo 1.6 )] indicate that Santa Luica (2008) is a member of the low iron L chondrite group, corresponding to the equilibrated petrologic type 6. The meteorite name was approved by the Nomenclature Committee (NomCom) of the Meteoritical Society (Meteoritic Bulletin, no. 97). We report about the chemical composition of the major mineral phases, its bulk trace element abundance, its noble gas and nitrogen data. The cosmic ray exposure age based on cosmogenic 3 He, 21 Ne, and 38 Ar around 20 Ma is comparable to one peak of L chondrites. The radiogenic K–Ar age of 2.96 Ga, while the young U, Th–He are of 1.2 Ga indicates that Santa Lucia (2008) lost radiogenic 4 He more recently. Low cosmogenic ( 22 Ne/ 21 Ne) c and absence of solar wind noble gases are consistent with irradiation in a large body. Heavy noble gases (Ar/Kr/Xe) indicated trapped gases similar to ordinary chondrites. Krypton and neon indicates irradiation in large body, implying large pre-atmospheric meteoroid.
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    Electronic ISSN: 1573-0794
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  • 2
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    Erratum to: Temporal Development of HF-Excited Langmuir and Ion Turbulence at Arecibo (2015)
    Springer
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    Publication Date: 2015-10-21
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  • 3
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    Interaction of Low-Activity Comets with the Solar Wind (2015)
    Springer
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    Publication Date: 2015-09-15
    Description: The solar wind flow around a cometary atmosphere is calculated using the three-dimensional magnetohydrodynamic model developed by the authors. Emphasis is placed on the case of low-activity comets in which some special features, both quantitative and qualitative, are inherent. The behavior of the flowfield and the magnetic field disturbed by the cometary outflow is analyzed. Some similarity laws that govern the pattern of the interaction between the solar wind and a cometary atmosphere are derived on the basis of the calculated results.
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  • 4
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    Modeled Interaction of Comet 67P/Churyumov-Gerasimenko with the Solar Wind Inside 2 AU (2015)
    Springer
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    Publication Date: 2015-08-18
    Description: Periodic comets move around the Sun on elliptical orbits. As such comet 67P/Churyumov-Gerasimenko (hereafter 67P) spends a portion of time in the inner solar system where it is exposed to increased solar insolation. Therefore given the change in heliocentric distance, in case of 67P from aphelion at 5.68 AU to perihelion at ~1.24 AU, the comet’s activity—the production of neutral gas and dust—undergoes significant variations. As a consequence, during the inbound portion, the mass loading of the solar wind increases and extends to larger spatial scales. This paper investigates how this interaction changes the character of the plasma environment of the comet by means of multifluid MHD simulations. The multifluid MHD model is capable of separating the dynamics of the solar wind ions and the pick-up ions created through photoionization and electron impact ionization in the coma of the comet. We show how two of the major boundaries, the bow shock and the diamagnetic cavity, form and develop as the comet moves through the inner solar system. Likewise for 67P, although most likely shifted back in time with respect to perihelion passage, this process is reversed on the outbound portion of the orbit. The presented model herein is able to reproduce some of the key features previously only accessible to particle-based models that take full account of the ions’ gyration. The results shown herein are in decent agreement to these hybrid-type kinetic simulations.
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  • 5
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    Low Speed Granular–Granular Impact Crater Opening Mechanism in 2D Experiments (2015)
    Springer
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    Publication Date: 2015-08-14
    Description: Quasi-2D, low-velocity experiments of colliding granular projectiles against granular targets were performed by means of a 7 m-long Hele-Shaw cell. The processes involved in the crater-opening mechanism of low-velocity granular-against-granular collisions are described. We show that the crater is opened mainly by a compaction process of the target. The projectile is fragmented and its lower section suffers a severe compaction; this projectile remnant forms a central dome or peak inside the crater. When the target reaches its maximum degree of compaction, the excess of momentum generates fast avalanches sliding on the slopes of the confined material, and exerts pressure on the crater walls, increasing its diameter. We propose that low-velocity collisions between granular aggregates are a possible mechanism that allows the growth of small planetary objects or the aggregation after catastrophic or high-energy collisions.
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  • 6
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    Automatic Analysis of Radio Meteor Events Using Neural Networks (2015)
    Springer
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    Publication Date: 2015-07-18
    Description: Meteor Scanning Algorithms (MESCAL) is a software application for automatic meteor detection from radio recordings, which uses self-organizing maps and feedforward multi-layered perceptrons. This paper aims to present the theoretical concepts behind this application and the main features of MESCAL, showcasing how radio recordings are handled, prepared for analysis, and used to train the aforementioned neural networks. The neural networks trained using MESCAL allow for valuable detection results, such as high correct detection rates and low false-positive rates, and at the same time offer new possibilities for improving the results.
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  • 7
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    A Spectral and Morphometric Analysis of a Small Lunar Dome Complex Blanketed by Ejecta in Euclides-J Region (2015)
    Springer
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    Publication Date: 2015-06-09
    Description: This study focuses on a relatively unexplored area located some 33.4 geodetic km away from the central floor of Euclides, in the NE direction, precisely at −6.62° Latitude and −29.89° Longitude. Land-based CCD observations of this area showed a small group of dome-like structures situated on an elevated basaltic platform. One hypothesis is that these features represent a series of mounds made up of a collection of undifferentiated crater materials or ejecta as described by USGS (Geologic Atlas of the Moon. Department of Interior, US Geological Survey—I-458, 1965 ). This hypothesis is tested against an alternative one in that the area shows the presence of domes that are partly covered by these ejecta. The present spectrometric results place the basalt within the chosen AOI subset in the low-Ti category (1–5 wt% TiO 2 ) and a FeO abundance wt% of between 12 and 14. Spectrometrically, similar dome features have been observed by other investigators near the Milichus/Tobias Mayer regions. A possible classification for this feature would be DW/1a/6h/8j. Details of the cluster analysis used for raster classification is presented as an effective approach to discriminate between different classes of the lunar surface. This approach was used to map the lunar soil geology over the selected showing better lunar geological information than the current mapping information available by USGS. This same approach can be used to effectively map out other regions of the lunar surface.
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  • 8
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    Simultaneous Multi-angle Observations of Strong Langmuir Turbulence at HAARP (2015)
    Springer
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    Publication Date: 2015-06-04
    Description: We report results from a recent series of experiments employing the HF transmitter of the High Frequency Active Auroral Research Program (HAARP) to generate and study strong Langmuir turbulence (SLT) in the interaction region of overdense ionospheric plasma. The Modular UHF Ionospheric Radar (MUIR) located at the HAARP facility is used as the primary diagnostic. Short pulse, low duty cycle experiments are used to avoid generation of artificial field-aligned irregularities and isolate ponderomotive plasma turbulence effects. The HF pump frequency is close to the 3rd gyro-harmonic frequency and the HF pointing angle and MUIR look angle are between the HF Spitze angle and Magnetic Zenith angle. Plasma line spectra measured simultaneously in different spots of the interaction region display differences dependent on the aspect angle of the HF pump beam in the boresight direction and the pointing angle of the MUIR diagnostic radar. Outshifted Plasma Lines, cascade, collapse, coexistence, spectra are observed in agreement with existing theory and simulation results of Strong Langmuir Turbulence in ionospheric interaction experiments. It is found that SLT at HAARP is most readily observed at a HF pointing angle of 11° and UHF observation angle of 15°, which is consistent with the magnetic zenith effect as documented in previous works and optimal orientation of the refracted HF electric field vector.
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  • 9
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    Circular Polarization Characteristics of South Polar Lunar Craters using Chandrayaan-1 Mini-SAR and LRO Mini-RF (2015)
    Springer
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    Publication Date: 2015-05-10
    Description: The paper presents a case study of inconsistent behaviour of Chandrayaan-1 Mini-SAR and LRO Mini-RF data over south polar lunar craters. The paper includes analysis of Stokes parameters and characterization of received time-varying electromagnetic fields over the south pole lunar craters. For the study, Chandrayaan-1 Mini-SAR and LRO Mini-RF data at 2.38 GHz are used. Total five lunar craters in south polar region are analyzed to study the effect of various parameters on the polarization of the signal. We have compared linear horizontal (LH) and linear vertical (LV) polarization components of received radar signal over the same targets using two different SAR data. Ratios of received LH to LV components are also derived over the five craters. It is observed that Chandrayaan-1 Mini-SAR is receiving high LH component as compared to LV component. This is not consistent with the scattering theory (Fawwaz et al. in Microwave remote sensing active and passive, Artech House Inc., New York, 1981 ), which states that for incidence angle greater than 15°, the vertical polarized component of a received signal should be always high as compared to horizontal polarized component over rough surfaces. These inconsistent results of Chandrayaan-1 Mini-SAR are observed over all five craters. In the paper, various effects of sensor parameters like incident angle, ellipticity angle, orientation angle etc. on scattering mechanism are discussed to understand the inconsistent behaviour of two SAR data over same target.
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  • 10
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    Ca-, Al-Rich Inclusions in Two New Carbonaceous Chondrites from Grove Mountains, Antarctica (2015)
    Springer
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    Publication Date: 2015-05-09
    Description: Two new carbonaceous chondrites, GRV 023155 and GRV 050179, collected from the Grove Mountains (GRV), Antarctica, have been classified as the oxidized CV3 and CM2 chondrites, respectively.  A total of 9 Ca-, Al-rich inclusions (CAIs) were found in the two meteorites. Most of the inclusions are extensively altered, with phyllosilicates commonly found in the alteration assemblages of CAIs, chondrules and matrix in the GRV 050179 CM2 chondrites, suggesting that aqueous alteration occurred on the host meteorite parent body. In contrast, feldspathoids and hedenbergite were identified in the CAIs from GRV 023155. The FeO-rich phases in the CAIs from GRV 023155 indicate alteration of these CAIs happened under high oxygen fugacity. All 9 inclusions can be classified as Type A or spinel-pyroxene rich inclusions, and they probably represent a continuum of solar nebular condensation. The survey of Ca-, Al-rich inclusions in GRV 023155 (CV3) and 050179 (CM2) suggests that Type A and spinel-pyroxene inclusions are common in these two meteorites.
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