Journal article
ARTEMIS observations of the solar wind proton scattering function from lunar crustal magnetic anomalies
Journal of geophysical research. Planets, Vol.122(4), pp.771-783
04/2017
DOI: 10.1002/2017JE005313
PMCID: PMC7802739
PMID: 33442502
Abstract
Despite their small scales, lunar crustal magnetic fields are routinely associated with observations of reflected and/or backstreaming 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 (Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun) 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 unmagnetized surface reflects between 0.1 and 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.
Key Points
ARTEMIS regularly observes protons reflected from lunar crustal magnetic fields
Reflected protons traced from ARTEMIS to lunar surface to compile the global reflection map and scattering function
Scattering function consistent with electrostatic fields as reflection mechanism from anomalies
Details
- Title: Subtitle
- ARTEMIS observations of the solar wind proton scattering function from lunar crustal magnetic anomalies
- Creators
- A. R Poppe - University of California, BerkeleyJ. S Halekas - University of IowaC Lue - University of IowaS Fatemi - University of California, Berkeley
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Planets, Vol.122(4), pp.771-783
- DOI
- 10.1002/2017JE005313
- PMID
- 33442502
- PMCID
- PMC7802739
- ISSN
- 2169-9097
- eISSN
- 2169-9100
- Number of pages
- 13
- Grant note
- German Center for Aviation and Space (DLR) (50 OC 0302) NASA (NNX15AP89G; NAS5-02099)
- Language
- English
- Date published
- 04/2017
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199944402771
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