Publication Date:
2017-04-19
Description:
We report on the properties of suprathermal electrons observed over three discrete auroral arcs from a sounding rocket by applying shifted kappa distributions. By analyzing kappa parameters (density, temperature, and kappa), we found three novel characteristics to provide clues to understanding the auroral acceleration mechanisms and magnetosphere-ionosphere coupling processes. First, the auroral potential drop was proportional to the inverse-square of kappa, consistent with previous theoretical investigations by [ Dors and Kletzing , 1999]. The observed dependency was slightly stronger than their calculations, suggesting additional contribution from non-linear plasma processes. Second, the polytropic relation showed non-adiabatic (near isothermal) state of the source electrons. This can provide a restriction on the pressure balance issues in the plasma sheet convection. Third, there was a clear difference in the polytropic and the kappa index for the first arc as opposed to the second and the third arcs, suggesting different source locations in the plasma sheet for precipitating electrons to cause these near-by arcs.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics
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