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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 23, issue 4
Ann. Geophys., 23, 1249–1258, 2005
https://doi.org/10.5194/angeo-23-1249-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 23, 1249–1258, 2005
https://doi.org/10.5194/angeo-23-1249-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.

  03 Jun 2005

03 Jun 2005

Excitation of plasma waves by unstable photoelectron and thermal electron populations on closed magnetic field lines in the Martian ionosphere

N. Borisov1,2 and E. Nielsen2 N. Borisov and E. Nielsen
  • 1Institute of Terrestrial Magnetism, Ionosphere and Radio Waves propagation, 142190, Troitsk, Russia
  • 2Max-Planck Institut für Sonnensystemforschung, D-37191 Katlenburg-Lindau, Germany

Abstract. 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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