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EMIC Waves in the Outer Magnetosphere: Observations of an Off‐Equator Source Region
Author(s) -
Vines S. K.,
Allen R. C.,
Anderson B. J.,
Engebretson M. J.,
Fuselier S. A.,
Russell C. T.,
Strangeway R. J.,
Ergun R. E.,
Lindqvist P. A.,
Torbert R. B.,
Burch J. L.
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl082152
Subject(s) - equator , magnetosphere , geophysics , physics , poynting vector , cyclotron , magnetic field , wave packet , magnetic dip , geology , latitude , computational physics , astronomy , atomic physics , quantum mechanics
Electromagnetic ion cyclotron (EMIC) waves at large L shells were observed away from the magnetic equator by the Magnetospheric MultiScale (MMS) mission nearly continuously for over four hours on 28 October 2015. During this event, the wave Poynting vector direction systematically changed from parallel to the magnetic field (toward the equator), to bidirectional, to antiparallel (away from the equator). These changes coincide with the shift in the location of the minimum in the magnetic field in the southern hemisphere from poleward to equatorward of MMS. The local plasma conditions measured with the EMIC waves also suggest that the outer magnetospheric region sampled during this event was generally unstable to EMIC wave growth. Together, these observations indicate that the bidirectionally propagating wave packets were not a result of reflection at high latitudes but that MMS passed through an off‐equator EMIC wave source region associated with the local minimum in the magnetic field.