Location of intense electromagnetic ion cyclotron (EMIC) wave events relative to the plasmapause: Van Allen Probes observations

Journal Article · Fri Mar 17 00:00:00 EDT 2017 · Journal of Geophysical Research. Space Physics

DOI: https://doi.org/10.1002/2016JA023392 · OSTI ID:1402621

Tetrick, S. S.  ^[1]; Engebretson, M. J.  ^[2]; Posch, J. L.  ^[2]; Olson, C. N. ^[2]; Smith, C. W.  ^[3]; Denton, R. E.  ^[4]; Thaller, S. A.  ^[5]; Wygant, J. R.  ^[5]; Reeves, G. D.  ^[6]; MacDonald, E. A.  ^[7]; Fennell, J. F.  ^[8]

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1. Augsburg College, Minneapolis, MN (United States). Dept. of Physics; Univ. of Iowa, Iowa City, IA (United States). Dept. of Physics and Astronomy
2. Augsburg College, Minneapolis, MN (United States). Dept. of Physics
3. Univ. of New Hampshire, Durham, NH (United States). Space Science Center
4. Dartmouth College, Hanover, NH (United States). Dept. of Physics and Astronomy
5. Univ. of Minnesota, Minneapolis, MN (United States). School of Physics and Astronomy
6. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
7. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
8. The Aerospace Corporation, Los Angeles, CA (United States)

In this paper, we have studied the spatial location relative to the plasmapause (PP) of the most intense electromagnetic ion cyclotron (EMIC) waves observed on Van Allen Probes A and B during their first full precession in local time. Most of these waves occurred over an L range of from -1 to +2 R_E relative to the PP. Very few events occurred only within 0.1 R_E of the PP, and events with a width in L of < 0.2 R_E occurred both inside and outside the PP. Wave occurrence was always associated with high densities of ring current ions; plasma density gradients or enhancements were associated with some events but were not dominant factors in determining the sites of wave generation. Storm main and recovery phase events in the dusk sector were often inside the PP, and dayside events during quiet times and compressions of the magnetosphere were more evenly distributed both inside and outside the PP. Superposed epoch analyses of the dependence of wave onset on solar wind dynamic pressure (Psw), the SME (SuperMAG auroral electrojet) index, and the SYM-H index showed that substorm injections and solar wind compressions were temporally closely associated with EMIC wave onset but to an extent that varied with frequency band, magnetic local time, and storm phase, and location relative to the PP. Finally, the fact that increases in SME and Psw were less strongly correlated with events at the PP than with other events might suggest that the occurrence of those events was affected by the density gradient.

• Research Organization: Augsburg College, Minneapolis, MN (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States); NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
• Sponsoring Organization: USDOE; National Science Foundation (NSF) (United States); National Aeronautics and Space Administration (NASA) (United States)
• Grant/Contract Number: AC52-06NA25396
• OSTI ID: 1402621
• Report Number(s): LA-UR--17-20105
• Journal Information: Journal of Geophysical Research. Space Physics, Journal Name: Journal of Geophysical Research. Space Physics Journal Issue: 4 Vol. 122; ISSN 2169-9380
• Publisher: American Geophysical UnionCopyright Statement
• Country of Publication: United States
• Language: English