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Observations of energetic particle escape at the magnetopause: Early results from the MMS Energetic Ion Spectrometer (EIS)
Author(s) -
Cohen I. J.,
Mauk B. H.,
Anderson B. J.,
Westlake J. H.,
Sibeck D. G.,
Giles B. L.,
Pollock C. J.,
Turner D. L.,
Fennell J. F.,
Blake J. B.,
Clemmons J. H.,
Jaynes A. N.,
Baker D. N.,
Craft J. V.,
Spence H. E.,
Niehof J. T.,
Reeves G. D.,
Torbert R. B.,
Russell C. T.,
Strangeway R. J.,
Magnes W.,
Trattner K. J.,
Fuselier S. A.,
Burch J. L.
Publication year - 2016
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 - 10.1002/2016gl068689
Subject(s) - magnetosheath , magnetopause , magnetosphere , physics , pitch angle , geophysics , electron , solar wind , computational physics , astrophysics , magnetic field , quantum mechanics
Energetic (greater than tens of keV) magnetospheric particle escape into the magnetosheath occurs commonly, irrespective of conditions that engender reconnection and boundary‐normal magnetic fields. A signature observed by the Magnetospheric Multiscale (MMS) mission, simultaneous monohemispheric streaming of multiple species (electrons, H + , He n + ), is reported here as unexpectedly common in the dayside, dusk quadrant of the magnetosheath even though that region is thought to be drift‐shadowed from energetic electrons. This signature is sometimes part of a pitch angle distribution evolving from symmetric in the magnetosphere, to asymmetric approaching the magnetopause, to monohemispheric streaming in the magnetosheath. While monohemispheric streaming in the magnetosheath may be possible without a boundary‐normal magnetic field, the additional pitch angle depletion, particularly of electrons, on the magnetospheric side requires one. Observations of this signature in the dayside dusk sector imply that the static picture of magnetospheric drift‐shadowing is inappropriate for energetic particle dynamics in the outer magnetosphere.