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| Titel |
Excitation of plasma waves by unstable photoelectron and thermal electron populations on closed magnetic field lines in the Martian ionosphere |
| VerfasserIn |
N. Borisov, E. Nielsen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 23, no. 4 ; Nr. 23, no. 4 (2005-06-03), S.1249-1258 |
| Datensatznummer |
250015220
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| Publikation (Nr.) |
 copernicus.org/angeo-23-1249-2005.pdf |
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| Zusammenfassung |
| It is argued that anisotropic electron
pitch angle distributions in the closed magnetic field regions
of the Martian ionosphere gives rise to excitation of plasma
instabilities. We discuss two types of instabilities that are excited
by two different populations of electrons. First, the generation
of Langmuir waves by photoelectrons with energies
of the order of 10eV is investigated. It is predicted that the
measured anisotropy of their pitch angle distribution at the heights
z≈400km causes
excitation of waves with frequencies f~30kHz and wavelengths λ~30m.
Near the terminators the instability of the electrostatic waves
with frequencies of the order of or less than the electron gyrofrequency
exited by thermal electrons is predicted.
The typical frequencies of these waves depend on the local
magnitude of the magnetic field and can achieve values f~3-5kHz
above strong crustal magnetic fields. |
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