Driving ionospheric outflows and magnetospheric O+ energy density with Alfvén waves. Issue 10 (28th May 2016)

• Record Type: Journal Article
• Authors: Chaston, C. C.; Bonnell, J. W.; Reeves, G. D.; Skoug, R. M.
• Is Part Of: Geophysical research letters. Volume 43:Issue 10(2016)
• Page Start: 4825
• Page End: 4833
• Publication Date: 2016-05-28
• Subjects: Alfvén waves -- ion acceleration -- ring current -- ionosphere -- ionospheric outflow; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2016GL069008
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: We show how dispersive Alfvén 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 "shock" 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 Alfvén 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. Key Points: Dispersive Alfvén waves extract O + ions from the topside ionosphere and drive these ions into the equatorial plane Dispersive Alfvén waves accelerate ionospheric O + to > 50 keV in the equatorial plane Dispersive Alfvén wave ion acceleration may account for large O + contributions to the storm time ring current