Journal article
Lunar surface charging during solar energetic particle events: Measurement and prediction
Journal of Geophysical Research: Space Physics, Vol.114(A5), A05110
05/2009
DOI: 10.1029/2009JA014113
Abstract
[1] We analyzed lunar surface charging during solar energetic particle (SEP) events, utilizing Lunar Prospector measurements of surface potentials and electron fluxes, and upstream energetic particle data. Outside of the magnetosphere, we find a nearly one-to-one correspondence between extreme negative lunar surface charging and large solar proton events. Using new techniques to correct for spacecraft potential, we present the first quantitative measurements of lunar charging during SEP events, during which we find that the nightside surface reaches potentials of up to −4.5 kV, with negative potentials of a kilovolt or larger often observed. These potentials are far higher than typical nightside potentials of a few hundred volts negative and may increase the risk of electrostatic discharge and/or dust effects, introducing an additional hazard to the already dangerous radiation environment. For eight of eleven event periods, surface potentials correlate with electron temperature and with the ratio of energetic electron flux to both energetic proton flux and total electron flux. For these eight events, charging models taking into account both thermal/suprathermal and energetic particle fluxes, as well as secondary emission, can successfully predict surface potentials. However, during the other three events, surface potentials do not correlate with the same measurable quantities, and charging models cannot reproduce measured potentials. In order to develop reliable and accurate models for lunar surface charging during SEP events, we will need better measurements of ion and energetic particle behavior in the lunar environment, secondary electron emission from lunar materials, and lunar surface potentials.
Details
- Title: Subtitle
- Lunar surface charging during solar energetic particle events: Measurement and prediction
- Creators
- J. S Halekas - University of California, BerkeleyG. T Delory - University of California, BerkeleyR. P Lin - University of California, BerkeleyT. J Stubbs - University of Maryland, BaltimoreW. M Farrell - Goddard Space Flight Center
- Resource Type
- Journal article
- Publication Details
- Journal of Geophysical Research: Space Physics, Vol.114(A5), A05110
- DOI
- 10.1029/2009JA014113
- ISSN
- 0148-0227
- eISSN
- 2156-2202
- Publisher
- Blackwell Publishing Ltd
- Number of pages
- 16
- Language
- English
- Date published
- 05/2009
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199930502771
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