Origin of Earth's diffuse aurora (Invited)

Details Origin of Earth's diffuse aurora (Invited) Origin of Earth's diffuse aurora (Invited)

Dec 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsm14b..01t&link_type=abstract

American Geophysical Union, Fall Meeting 2010, abstract #SM14B-01

Physics

[2716] Magnetospheric Physics / Energetic Particles: Precipitating, [2772] Magnetospheric Physics / Plasma Waves And Instabilities

Scientific paper

Earth’s diffuse aurora occurs over a broad latitude range and is primarily caused by the precipitation of low-energy (100 eV-30 keV) electrons originating from the central plasma sheet. Although generally subvisual, the diffuse auroral precipitation provides the major source of energy input for the high-latitude night-side upper atmosphere, leading to enhanced ionization and chemical change. Previous theoretical studies have indicated that two distinct classes of magnetospheric plasma waves, electrostatic electron cyclotron harmonic waves and whistler-mode chorus waves, could be responsible for electron scattering leading to diffuse auroral precipitation, but it has not previously been possible to determine which waves are the most important. Here we show, by detailed analysis of satellite wave data and by Fokker-Planck diffusion calculations, that scattering by chorus is the dominant cause of the most intense diffuse auroral precipitation. This resolves a long-standing controversy in magnetospheric physics. Furthermore, scattering by chorus can remove the majority of injected plasma sheet electrons as they are transported from the nightside to the dayside, thus accounting for the global morphology of the diffuse aurora. The scattering by chorus also leads to the development of observed pancake distributions at energies below a few keV, and enhanced pitch angle anisotropy at energies above 10 keV. Such electron distributions can sustain the excitation of upper and lower band chorus over a broad range of MLT between 2100 and the dayside.

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