Journal article
MAVEN observations of electron‐induced whistler mode waves in the Martian magnetosphere
Journal of geophysical research. Space physics, Vol.121(10), pp.9717-9731
10/2016
DOI: 10.1002/2016JA023194
Abstract
We report on narrowband electromagnetic waves at frequencies between the local electron cyclotron and lower hybrid frequencies observed by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft in the Martian induced magnetosphere. The peaked electric field wave spectra below the electron cyclotron frequency were first observed by Phobos‐2 in the Martian magnetosphere, but the lack of magnetic field wave data prevented definitive identification of the wave mode and their generation mechanisms remain unclear. Analysis of electric and magnetic field wave spectra obtained by MAVEN demonstrates that the observed narrowband waves have properties consistent with the whistler mode. Linear growth rates computed from the measured electron velocity distributions suggest that these whistler mode waves can be generated by cyclotron resonance with anisotropic electrons. Large electron anisotropy in the Martian magnetosphere is caused by absorption of parallel electrons by the collisional atmosphere. The narrowband whistler mode waves and anisotropic electrons are observed on both open and closed field lines and have similar spatial distributions in MSO and planetary coordinates. Some of the waves on closed field lines exhibit complex frequency‐time structures such as discrete elements of rising tones and two bands above and below half the electron cyclotron frequency. These MAVEN observations indicate that whistler mode waves driven by anisotropic electrons, which are commonly observed in intrinsic magnetospheres and at unmagnetized airless bodies, are also present at Mars. The wave‐induced electron precipitation into the Martian atmosphere should be evaluated in future studies.
Key Points
MAVEN observes narrowband whistler mode waves in the Martian magnetosphere
The whistler mode waves are generated by cyclotron resonance with anisotropic electrons
The whistler mode waves could play a role in electron precipitation into the Martian atmosphere
Details
- Title: Subtitle
- MAVEN observations of electron‐induced whistler mode waves in the Martian magnetosphere
- Creators
- J. S Halekas - University of IowaY Harada - University of California, BerkeleyL Andersson - University of Colorado BoulderS Xu - University of California, BerkeleyC. M Fowler - University of Colorado BoulderD. L Mitchell - University of California, BerkeleyC Mazelle - Centre National pour la Recherche Scientifique et Technique (CNRST)J Espley - Goddard Space Flight CenterG. A DiBraccio - Goddard Space Flight CenterJ. P McFadden - University of California, BerkeleyD. A Brain - University of Colorado BoulderS Ruhunusiri - University of IowaD. E Larson - University of California, BerkeleyR. J Lillis - University of California, BerkeleyT Hara - University of California, BerkeleyR Livi - University of California, BerkeleyB. M Jakosky - University of Colorado Boulder
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Space physics, Vol.121(10), pp.9717-9731
- DOI
- 10.1002/2016JA023194
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Number of pages
- 15
- Grant note
- NASA CNES
- Language
- English
- Date published
- 10/2016
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199830802771
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