Open AccessComments on Vasyliunas' and Pontius' studies of the effects of the planetary ionosphere and of the Coriolis force on the interchange instability
Author(s) -
André N.,
Ferrière K. M.
Publication year - 2007
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2006ja011732
Subject(s) - instability , magnetosphere , physics , ionosphere , plasma , electric field , magnetic field , geophysics , mechanics , classical mechanics , computational physics , quantum mechanics
Recent Galileo and Cassini plasma and magnetic field observations indicate that the centrifugal/interchange instability plays a critical role in radial plasma transport in the rapidly rotating magnetospheres of giant planets. These observations have stimulated considerable interest in understanding the development and the properties of the instability. A complete description of the interchange instability involves an electric coupling between the magnetosphere and the planetary ionosphere. Vasyliunas (1994) pointed out that when the ionosphere is ineffective at constraining interchange motions, local magnetospheric conditions govern the plasma dynamics. In that case the Coriolis force leads to a dramatic decrease in the instability growth rate according to Pontius (1997), whereas it has a neutral influence according to Ferrière et al. (2001). The purpose of the present paper is to critically reexamine Vasyliunas' and Pontius' results and investigate the origin of their discrepancies with Ferrière et al.'s results. To that end, we consider the case of a thin plasma disk in an axisymmetric, rapidly rotating magnetosphere with no field‐aligned electric currents at equilibrium.