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Firehose driven magnetic fluctuations in the magnetosphere
Author(s) -
Horton W.,
Xu B.Y.,
Wong H. Ver
Publication year - 2004
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 - 10.1029/2003gl018309
Subject(s) - physics , magnetosphere , amplitude , plasma sheet , plasma , magnetic field , instability , adiabatic process , earth's magnetic field , curvature , nonlinear system , quantum electrodynamics , computational physics , mechanics , quantum mechanics , geometry , mathematics
The nonlinear saturation of the firehose instability in the high plasma pressure central plasma sheet is shown to produce a wide spectrum of Alfvénic fluctuations in the range of Pi‐2 geomagnetic pulsations. The wave energy sources are the small p ∥ / p ⊥ > 1 + B 2 /μ 0 p ⊥ anisotropies which are created by Earthward ion convection at constant first and second adiabatic invariants. In the nonlinear state, the field‐line curvature force is weaker than the linear force. This weakening of the driving force limits the amplitude of the Alfvénic fluctuations. Away from the equatorial plane, the plasma is firehose stable, but carries large magnetic fluctuations.