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Observations of Sounder Accelerated Electrons by Mars Express
Author(s) -
Barabash S.,
Voshchepynets A.,
Holmstrom M.,
Frahm R. A.,
Nillsson H.,
Andrews D.,
Kopf A.,
Winningham J. D.
Publication year - 2020
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2019ja027206
Subject(s) - electron , mars exploration program , physics , ionosphere , sounding rocket , spacecraft , solar wind , spacecraft charging , atomic physics , plasma , computational physics , geophysics , nuclear physics , astrobiology , astronomy
The electron sensor of the Analyzer of Space Plasmas and Energetic Atoms experiment detects accelerated electrons during pulses of radio emissions from the powerful topside sounder: the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on board the Mars Express spacecraft. Accelerated electrons are observed at energies up to 400 eV at the times when MARSIS transmits at a frequency between the local plasma frequency and its harmonics (up to 4 times the plasma frequency). When the electron density and magnetic field strength are low ( ∼ 1 0 3 cm− 3 , ∼ 10 nT), the accelerated electrons are almost monoenergetic electron beams. An increase in density and magnetic field ( ∼ 3 · 1 0 3 cm− 3 , ∼ 50 nT) leads to substantial broadening of the energy spectrum of the accelerated electrons. It is concluded that in the latter case, electrons are accelerated by the variable spacecraft potential resulting from the imbalance of the electron and ion currents to the MARSIS antenna during transmission.