“Trunk-like” heavy ion structures observed by the Van Allen Probes

Title“Trunk-like” heavy ion structures observed by the Van Allen Probes
Publication TypeJournal Article
Year of Publication2015
AuthorsZhang, J-C, Kistler, LM, Spence, HE, Wolf, RA, Reeves, G, Skoug, R, Funsten, H, Larsen, BA, Niehof, JT, MacDonald, EA, Friedel, R, Ferradas, CP, Luo, H
JournalJournal of Geophysical Research: Space Physics
Date Published10/2015
Keywordsinner magnetosphere; ion injection; Ion structure; magnetic cloud; magnetic storm; Van Allen Probes
AbstractDynamic ion spectral features in the inner magnetosphere are the observational signatures of ion acceleration, transport, and loss in the global magnetosphere. We report “trunk-like” ion structures observed by the Van Allen Probes on 2 November 2012. This new type of ion structure looks like an elephant's trunk on an energy-time spectrogram, with the energy of the peak flux decreasing Earthward. The trunks are present in He+ and O+ ions but not in H+. During the event, ion energies in the He+ trunk, located at L = 3.6–2.6, MLT = 9.1–10.5, and MLAT = −2.4–0.09°, vary monotonically from 3.5 to 0.04 keV. The values at the two end points of the O+ trunk are: energy = 4.5–0.7 keV, L = 3.6–2.5, MLT = 9.1–10.7, and MLAT = −2.4–0.4°. Results from backward ion drift path tracings indicate that the trunks are likely due to 1) a gap in the nightside ion source or 2) greatly enhanced impulsive electric fields associated with elevated geomagnetic activity. Different ion loss lifetimes cause the trunks to differ among ion species.
Short TitleJ. Geophys. Res. Space Physics

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