Nongyrotropic electron velocity distribution functions near the lunar surface

Yuki Harada, Shinobu Machida, Yoshifumi Saito, Shoichiro Yokota, Kazushi Asamura, Masaki N. Nishino, Hideo Tsunakawa, Hidetoshi Shibuya, Futoshi Takahashi, Masaki Matsushima, Hisayoshi Shimizu

Research output: Contribution to journalArticle

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Abstract

We have analyzed nongyrotropic electron velocity distribution functions (VDFs) obtained near the lunar surface. Electron VDFs, measured at 10-100 km altitude by Kaguya in both the solar wind and the Earth's magnetosphere, exhibit nongyrotropic empty regions associated with the 'gyroloss' effect; i.e., electron absorption by the lunar surface combined with electron gyromotion. Particle-trace calculations allow us to derive theoretical forbidden regions in the electron VDFs, thereby taking into account the modifications due to nonuniform magnetic fields caused by diamagnetic-current systems, lunar-surface charging, and electric fields perpendicular to the magnetic field. Comparison between the observed empty regions with the theoretically derived forbidden regions suggests that various components modify the characteristics of the nongyrotropic electron VDFs depending on the ambient-plasma conditions. On the lunar nightside in the magnetotail lobes, negative surface potentials slightly reduce the size of the forbidden regions, but there are no distinct effects of either the diamagnetic current or perpendicular electric fields. On the dayside in the solar wind, the observations suggest the presence of either the diamagnetic-current or solar wind convection electric field effects, or both. In the terrestrial plasma sheet, all three mechanisms can substantially modify the characteristics of the forbidden regions. The observations imply the presence of a local electric field of at least 5 mV/m although the mechanism responsible for production of such a strong electric field is unknown. Analysis of nongyrotropic VDFs associated with the gyroloss effect near solid surfaces can promote a better understanding of the near-surface plasma environment and of plasma-solid-surface interactions.

Original languageEnglish
Article numberA07220
JournalJournal of Geophysical Research: Space Physics
Volume117
Issue number7
DOIs
Publication statusPublished - Jan 1 2012
Externally publishedYes

Fingerprint

lunar surface
Velocity distribution
Distribution functions
electric field
velocity distribution
distribution functions
electrons
electron
Solar wind
Electrons
Electric fields
electric fields
solar wind
Plasmas
plasma
magnetic fields
solid surfaces
Electron absorption
surface interactions
Magnetic fields

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

Cite this

Harada, Y., Machida, S., Saito, Y., Yokota, S., Asamura, K., N. Nishino, M., ... Shimizu, H. (2012). Nongyrotropic electron velocity distribution functions near the lunar surface. Journal of Geophysical Research: Space Physics, 117(7), [A07220]. https://doi.org/10.1029/2012JA017642

Nongyrotropic electron velocity distribution functions near the lunar surface. / Harada, Yuki; Machida, Shinobu; Saito, Yoshifumi; Yokota, Shoichiro; Asamura, Kazushi; N. Nishino, Masaki; Tsunakawa, Hideo; Shibuya, Hidetoshi; Takahashi, Futoshi; Matsushima, Masaki; Shimizu, Hisayoshi.

In: Journal of Geophysical Research: Space Physics, Vol. 117, No. 7, A07220, 01.01.2012.

Research output: Contribution to journalArticle

Harada, Y, Machida, S, Saito, Y, Yokota, S, Asamura, K, N. Nishino, M, Tsunakawa, H, Shibuya, H, Takahashi, F, Matsushima, M & Shimizu, H 2012, 'Nongyrotropic electron velocity distribution functions near the lunar surface', Journal of Geophysical Research: Space Physics, vol. 117, no. 7, A07220. https://doi.org/10.1029/2012JA017642
Harada, Yuki ; Machida, Shinobu ; Saito, Yoshifumi ; Yokota, Shoichiro ; Asamura, Kazushi ; N. Nishino, Masaki ; Tsunakawa, Hideo ; Shibuya, Hidetoshi ; Takahashi, Futoshi ; Matsushima, Masaki ; Shimizu, Hisayoshi. / Nongyrotropic electron velocity distribution functions near the lunar surface. In: Journal of Geophysical Research: Space Physics. 2012 ; Vol. 117, No. 7.
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