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| Titel |
Effect of the solar-wind proton entry into the deepest lunar wake |
| VerfasserIn |
Masaki N. Nishino, Masaki Fujimoto, Yoshifumi Saito, Shoichiro Yokota, Yoshiya Kasahara, Hideo Tsunakawa, Toshio Terasawa |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250033566
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| Zusammenfassung |
| We study effect of the solar wind (SW) proton entry deep into the near-Moon wake that was
recently discovered by the SELENE mission. Because previous lunar-wake models are based
on electron domination, no effect of SW proton entry on the near-Moon wake environment
has been taken into account so far. Recent SELENE observations revealed that a part of the
SW protons are reflected at the lunar dayside surface and picked-up by the SW electric field
(Saito et al., GRL, 2008), and some of them access the deepest lunar wake; this process is
called type-II entry (Nishino et al., GRL, 2009). Here we show that the type-II entry of SW
protons forms proton-governed region (PGR) to drastically change the electromagnetic
environment of the lunar wake. Broadband electrostatic noise found in the PGR is
manifestation of electron two-stream instability, which is attributed to the counter-streaming
electrons absorbed from the ambient SW to maintain the quasi-neutrality. Acceleration of the
absorbed electrons up to ~1 keV means a superabundance of positive charges of
10-4–10-7 cm-3 in the near-Moon wake, which should be immediately canceled
out by the incoming high-speed electrons. This is a general phenomenon in the
lunar wake, because PGR does not necessarily require peculiar SW condition for its
formation. |
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