Driving ionospheric outflows and magnetospheric O <sup>+</sup> energy density with Alfv\ en waves

Author
Keywords
Abstract
We show how dispersive Alfv\ en waves observed in the inner magnetosphere during geomagnetic storms can extract O+ ions from the topside ionosphere and accelerate these ions to energies exceeding 50 keV in the equatorial plane. This occurs through wave trapping, a variant of \textquotedblleftshock\textquotedblright surfing, and stochastic ion acceleration. These processes in combination with the mirror force drive field-aligned beams of outflowing ionospheric ions into the equatorial plane that evolve to provide energetic O+ distributions trapped near the equator. These waves also accelerate preexisting/injected ion populations on the same field lines. We show that the action of dispersive Alfv\ en waves over several minutes may drive order of magnitude increases in O+ ion pressure to make substantial contributions to magnetospheric ion energy density. These wave accelerated ions will enhance the ring current and play a role in the storm time evolution of the magnetosphere.
Year of Publication
2016
Journal
Geophysical Research Letters
Volume
43
Number of Pages
4825-4833
Date Published
05/2016
URL
http://doi.wiley.com/10.1002/2016GL069008
DOI
10.1002/2016GL069008