Observation of Auroral-like Peaked Electron Distributions at Mars

Details Observation of Auroral-like Peaked Electron Distributions at Mars Observation of Auroral-like Peaked Electron Distributions at Mars

Dec 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufmsa53b1166b&link_type=abstract

American Geophysical Union, Fall Meeting 2005, abstract #SA53B-1166

Physics

2780 Solar Wind Interactions With Unmagnetized Bodies, 5408 Aurorae And Airglow, 5421 Interactions With Particles And Fields, 6225 Mars, 7807 Charged Particle Motion And Acceleration

Scientific paper

Aurorae have been observed throughout the solar system and are associated with regions where charged particles have access to an atmosphere along magnetic field lines. Though aurorae are most prominent on planets with global dipole magnetic fields (like Earth and Jupiter), the Mars Express spacecraft recently reported localized UV auroral emission at Mars, which lacks a global dipole but has strong crustal magnetic fields. The particles and mechanisms responsible for emission in this non-dipolar environment have not been previously identified, and their relation to aurorae elsewhere in the solar system is an important open question. In this presentation, we report nearly 13,000 observations by the Mars Global Surveyor MAG/ER experiment of auroral-like electron distributions which result in enhanced electron precipitation into the Martian atmosphere. The energy spectra are peaked at 0.1--3~keV, very similar to terrestrial auroral electrons. We find that they are observed either on magnetic field lines that connect the shocked solar wind to localized strong crustal magnetic fields or on adjacent closed field lines. Accelerated electrons are often associated with magnetic field rotations and electromagnetic wave activity in MGS data. Many of the spectra are capable of producing atmospheric emission with intensity comparable to the reported UV emission. External conditions control whether acceleration is likely to be observed by MGS, including the orientation of the solar wind magnetic field, solar wind pressure, and the orientation of Mars with respect to the solar wind flow. This direct solar wind control is similar to terrestrial cusp aurorae. Further, both the reported Mars Express emisison and many of the most energetic distributions occur during the passage of solar energetic particle events through the Martian system, suggesting that the enhanced particle fluxes and disturbed magnetic environment during solar storm contribute to the most intense emission.

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