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A R Poppe - One of the best experts on this subject based on the ideXlab platform.
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artemis observations of the solar wind proton scattering function from lunar crustal Magnetic Anomalies reflected lunar protons
Journal of Geophysical Research, 2017Co-Authors: A R Poppe, J S Halekas, Charles Lue, S FatemiAbstract:Despite their small scales, lunar crustal Magnetic fields are routinely associated with observations of reflected and/or back-streaming populations of solar wind protons. Solar wind proton reflection locally reduces the rate of space weathering of the lunar regolith, depresses local sputtering rates of neutrals into the lunar exosphere, and can trigger electroMagnetic waves and small-scale collisionless shocks in the near-lunar space plasma environment. Thus, knowledge of both the magnitude and scattering function of solar wind protons from Magnetic Anomalies is crucial in understanding a wide variety of planetary phenomena at the Moon. We have compiled 5.5 years of ARTEMIS observations of reflected protons at the Moon and used a Liouville tracing method to ascertain each proton's reflection location and scattering angles. We find that solar wind proton reflection is largely correlated with crustal Magnetic field strength, with Anomalies such as South Pole/Aitken Basin (SPA), Mare Marginis, and Gerasimovich reflecting on average 5-12% of the solar wind flux while the un-magnetized surface reflects between 0.1-1% in charged form. We present the scattering function of solar wind protons off of the SPA anomaly, showing that the scattering transitions from isotropic at low solar zenith angles to strongly forward-scattering at solar zenith angles near 90° . Such scattering is consistent with simulations that have suggested electrostatic fields as the primary mechanism for solar wind proton reflection from crustal Magnetic Anomalies.
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anisotropic solar wind sputtering of the lunar surface induced by crustal Magnetic Anomalies
Geophysical Research Letters, 2014Co-Authors: A R Poppe, J S Halekas, M Sarantos, G T Delory, Y SaitoAbstract:The lunar exosphere is generated by several processes each of which generates neutral distributions with different spatial and temporal variability. Solar wind sputtering of the lunar surface is a major process for many regolith-derived species and typically generates neutral distributions with a cosine dependence on solar zenith angle. Complicating this picture are remanent crustal Magnetic Anomalies on the lunar surface, which decelerate and partially reflect the solar wind before it strikes the surface. We use Kaguya maps of solar wind reflection efficiencies, Lunar Prospector maps of crustal field strengths, and published neutral sputtering yields to calculate anisotropic solar wind sputtering maps. We feed these maps to a Monte Carlo neutral exospheric model to explore three-dimensional exospheric anisotropies and find that significant anisotropies should be present in the neutral exosphere depending on selenographic location and solar wind conditions. Better understanding of solar wind/crustal anomaly interactions could potentially improve our results.
J S Halekas - One of the best experts on this subject based on the ideXlab platform.
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artemis observations of the solar wind proton scattering function from lunar crustal Magnetic Anomalies reflected lunar protons
Journal of Geophysical Research, 2017Co-Authors: A R Poppe, J S Halekas, Charles Lue, S FatemiAbstract:Despite their small scales, lunar crustal Magnetic fields are routinely associated with observations of reflected and/or back-streaming populations of solar wind protons. Solar wind proton reflection locally reduces the rate of space weathering of the lunar regolith, depresses local sputtering rates of neutrals into the lunar exosphere, and can trigger electroMagnetic waves and small-scale collisionless shocks in the near-lunar space plasma environment. Thus, knowledge of both the magnitude and scattering function of solar wind protons from Magnetic Anomalies is crucial in understanding a wide variety of planetary phenomena at the Moon. We have compiled 5.5 years of ARTEMIS observations of reflected protons at the Moon and used a Liouville tracing method to ascertain each proton's reflection location and scattering angles. We find that solar wind proton reflection is largely correlated with crustal Magnetic field strength, with Anomalies such as South Pole/Aitken Basin (SPA), Mare Marginis, and Gerasimovich reflecting on average 5-12% of the solar wind flux while the un-magnetized surface reflects between 0.1-1% in charged form. We present the scattering function of solar wind protons off of the SPA anomaly, showing that the scattering transitions from isotropic at low solar zenith angles to strongly forward-scattering at solar zenith angles near 90° . Such scattering is consistent with simulations that have suggested electrostatic fields as the primary mechanism for solar wind proton reflection from crustal Magnetic Anomalies.
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anisotropic solar wind sputtering of the lunar surface induced by crustal Magnetic Anomalies
Geophysical Research Letters, 2014Co-Authors: A R Poppe, J S Halekas, M Sarantos, G T Delory, Y SaitoAbstract:The lunar exosphere is generated by several processes each of which generates neutral distributions with different spatial and temporal variability. Solar wind sputtering of the lunar surface is a major process for many regolith-derived species and typically generates neutral distributions with a cosine dependence on solar zenith angle. Complicating this picture are remanent crustal Magnetic Anomalies on the lunar surface, which decelerate and partially reflect the solar wind before it strikes the surface. We use Kaguya maps of solar wind reflection efficiencies, Lunar Prospector maps of crustal field strengths, and published neutral sputtering yields to calculate anisotropic solar wind sputtering maps. We feed these maps to a Monte Carlo neutral exospheric model to explore three-dimensional exospheric anisotropies and find that significant anisotropies should be present in the neutral exosphere depending on selenographic location and solar wind conditions. Better understanding of solar wind/crustal anomaly interactions could potentially improve our results.
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initial mapping and interpretation of lunar crustal Magnetic Anomalies using lunar prospector magnetometer data
Journal of Geophysical Research, 2001Co-Authors: L L Hood, J S Halekas, A Zakharian, D L Mitchell, R P Lin, M H Acuna, A B BinderAbstract:Maps of relatively strong crustal Magnetic field Anomalies detected at low altitudes with the magnetometer instrument on Lunar Prospector are presented. On the lunar nearside, relatively strong Anomalies are mapped over the Reiner Gamma Formation on western Oceanus Procellarum and over the Rima Sirsalis rille on the southwestern border of Oceanus Procellarum. The main Rima Sirsalis anomaly does not correlate well with the rille itself but is centered over an Imbrian-aged smooth plains unit interpreted as primary or secondary basin ejecta. The stronger Reiner Gamma Anomalies correlate with the locations of both the main Reiner Gamma albedo marking and its northeastward extension. Both the Rima Sirsalis and the Reiner Gamma Anomalies are extended in directions approximately radial to the center of the Imbrium basin. This alignment suggests that Imbrium basin ejecta materials (lying in many cases beneath the visible mare surface) are the sources of the nearside Anomalies. If so, then the albedo markings associated with the stronger Refiner Gamma Anomalies may be consistent with a model involving Magnetic shielding of freshly exposed mare materials from the solar wind ion bombardment. Two regions of extensive Magnetic Anomalies are mapped in regions centered on the Ingenii basin on the south central farside and near the crater Gerasimovic on the southeastern farside. These regions are approximately antipodal to the Imbrium and Crisium basins, respectively. The Imbrium antipode anomaly group is the most areally extensive on the Moon, while the largest anomaly in the Crisium antipode group is the strongest detected by the Lunar Prospector magnetometer. A consideration of the expected antipodal effects of basin-forming impacts as well as a combination of sample data and orbital measurements on the nearside leads to the conclusion that the most probable sources of Magnetic Anomalies in these two regions are ejecta materials from the respective impacts. In both regions the strongest individual Anomalies correlate with swirl-like albedo markings of the Reiner Gamma class visible on available orbital photography.
Yoshifumi Futaana - One of the best experts on this subject based on the ideXlab platform.
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on vertical electric fields at lunar Magnetic Anomalies
Geophysical Research Letters, 2014Co-Authors: R Jarvinen, Markku Alho, Esa Kallio, Peter Wurz, S Barabash, Yoshifumi FutaanaAbstract:We study the interaction between a Magnetic dipole mimicking the Gerasimovich Magnetic anomaly on the lunar surface and the solar wind in a self-consistent 3-D quasi-neutral hybrid simulation where ions are modeled as particles and electrons as a charge-neutralizing fluid. Especially, we consider the origin of the recently observed electric potentials at lunar Magnetic Anomalies. An antimoonward Hall electric field forms in our simulation resulting in a potential difference of <300V on the lunar surface, in which the value is similar to observations. Since the hybrid model assumes charge neutrality, our results suggest that the electric potentials at lunar Magnetic Anomalies can be formed by decoupling of ion and electron motion even without charge separation.
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On vertical electric fields at lunar Magnetic Anomalies
Geophysical Research Letters, 2014Co-Authors: R Jarvinen, Markku Alho, Esa Kallio, Peter Wurz, S Barabash, Yoshifumi FutaanaAbstract:We study the interaction between a Magnetic dipole mimicking the Gerasimovich Magnetic anomaly on the lunar surface and the solar wind in a self-consistent 3-D quasi-neutral hybrid simulation where ions are modeled as particles and electrons as a charge-neutralizing fluid. Especially, we consider the origin of the recently observed electric potentials at lunar Magnetic Anomalies. An antimoonward Hall electric field forms in our simulation resulting in a potential difference of
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energetic neutral atom observations of Magnetic Anomalies on the lunar surface
Journal of Geophysical Research, 2012Co-Authors: Audrey Vorburger, Peter Wurz, S Barabash, Yoshifumi Futaana, Martin Wieser, M Holmstrom, Anil Bhardwaj, K AsamuraAbstract:[1] SARA, the Sub-KeV Atom Analyzer, on board Chandrayaan-1 recorded the first image of a minimagnetosphere above a lunar Magnetic anomaly using energetic neutral atoms (ENAs). It was shown that this magnetosphere, which is located near the Gerasimovich crater, is able to reduce the solar wind ion flux impinging onto the lunar surface by more than 50%. Following this first observation, we investigated all Magnetic Anomalies that are in the SARA data set. We searched for a possible correlation between the solar wind plasma parameters (dynamic pressure, Magnetic field), the local Magnetic field, and the reduction in the reflected hydrogen ENA flux (henceforth called shielding efficiency). Having analyzed all observations by SARA, we discovered that the Gerasimovich Magnetic anomaly is topologically a very simple, large-scale Magnetic structure, which is favorable for this kind of investigation. Most other Magnetic Anomalies on the lunar surface have more small-scale features in their Magnetic field structure, which complicates the interpretation of the observed data. We find a clear correlation between the plasma parameters and the shielding efficiency for the Gerasimovich case. For the other observed Anomalies only about half of the cases showed such a correlation. We therefore conclude that the solar wind ions-Magnetic anomaly interaction is in general more complex than in the Gerasimovich case.
M Horanyi - One of the best experts on this subject based on the ideXlab platform.
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electroMagnetic particle in cell simulations of the solar wind interaction with lunar Magnetic Anomalies
Physical Review Letters, 2014Co-Authors: Jan Deca, Andrey Divin, Giovanni Lapenta, Bertrand Lembege, Stefano Markidis, M HoranyiAbstract:We present the first three-dimensional fully kinetic and electroMagnetic simulations of the solar wind interaction with lunar crustal Magnetic Anomalies (LMAs). Using the implicit particle-in-cell ...
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characteristics of a plasma sheath in a Magnetic dipole field implications to the solar wind interaction with the lunar Magnetic Anomalies
Journal of Geophysical Research, 2012Co-Authors: M Horanyi, X Wang, Scott RobertsonAbstract:[1] The solar wind interaction with the lunar surface, especially in regions of crustal Magnetic Anomalies, remains of great interest for in situ plasma measurements. Small- scale laboratory experiments cannot reproduce the conditions near the lunar surface, but provide a unique opportunity to identify and examine several of the physical processes. We study plasma interaction with a Magnetic dipole field at an insulating surface in order to understand the effect of crustal Magnetic Anomalies on the solar wind–lunar surface interaction. In our experiments, electrons are magnetized with gyroradii r smaller than distances from the surface d (r d. The measured potential distribution shows a non-monotonic sheath above the surface and variations on the surface along the axis of the dipole field. The surface near the center of the dipole is charged more positively by ions as the electrons are Magnetically shielded away. A potential minimum is found in the shielding region between the surface and the bulk plasma due to collisional and Magnetic mirror trapping effects. Potential variations on the surface are the result of the inhomogeneity of the dipolar field, showing an enhancement of the electric field at the cusps. Enhanced electric fields in the regions of Magnetic Anomalies on the lunar surface may enhance the transport of small-sized charged dust particles, possibly explaining the formation of the lunar swirls.
R Jarvinen - One of the best experts on this subject based on the ideXlab platform.
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on vertical electric fields at lunar Magnetic Anomalies
Geophysical Research Letters, 2014Co-Authors: R Jarvinen, Markku Alho, Esa Kallio, Peter Wurz, S Barabash, Yoshifumi FutaanaAbstract:We study the interaction between a Magnetic dipole mimicking the Gerasimovich Magnetic anomaly on the lunar surface and the solar wind in a self-consistent 3-D quasi-neutral hybrid simulation where ions are modeled as particles and electrons as a charge-neutralizing fluid. Especially, we consider the origin of the recently observed electric potentials at lunar Magnetic Anomalies. An antimoonward Hall electric field forms in our simulation resulting in a potential difference of <300V on the lunar surface, in which the value is similar to observations. Since the hybrid model assumes charge neutrality, our results suggest that the electric potentials at lunar Magnetic Anomalies can be formed by decoupling of ion and electron motion even without charge separation.
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On vertical electric fields at lunar Magnetic Anomalies
Geophysical Research Letters, 2014Co-Authors: R Jarvinen, Markku Alho, Esa Kallio, Peter Wurz, S Barabash, Yoshifumi FutaanaAbstract:We study the interaction between a Magnetic dipole mimicking the Gerasimovich Magnetic anomaly on the lunar surface and the solar wind in a self-consistent 3-D quasi-neutral hybrid simulation where ions are modeled as particles and electrons as a charge-neutralizing fluid. Especially, we consider the origin of the recently observed electric potentials at lunar Magnetic Anomalies. An antimoonward Hall electric field forms in our simulation resulting in a potential difference of
