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Feedback and Ballooning Instabilities in the Magnetosphere‐Ionosphere Coupling
Author(s) -
Watanabe T.H.
Publication year - 2020
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 - 10.1029/2020gl088233
Subject(s) - ballooning , physics , magnetosphere , magnetohydrodynamic drive , ionosphere , instability , pressure gradient , magnetohydrodynamics , convection , coupling (piping) , mechanics , classical mechanics , geophysics , magnetic field , plasma , materials science , tokamak , quantum mechanics , metallurgy
A unified model for the feedback and ballooning instabilities in the magnetosphere‐ionosphere (M‐I) coupling is developed by means of the reduced magnetohydrodynamic and two‐fluid equations, involving the local current closure and the ionospheric conductivity change in a scale of auroral fine structures, self‐consistently. In a low pressure gradient case, the Alfvén harmonics are destabilized through the feedback mechanism, while the ballooning instability appears if the magnetospheric pressure gradient exceeds a critical value. Transition of the dominant instability between the feedback and ballooning modes is brought by change of the normalized pressure gradient or the convection electric field in the magnetosphere. The obtained results imply a variety of appearance of auroral arcs and beads in the M‐I coupling system.