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Ion heating and acceleration by magnetosonic waves via cyclotron subharmonic resonance
Author(s) -
Terasawa Toshio,
Nambu Mitsuhiro
Publication year - 1989
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/gl016i005p00357
Subject(s) - physics , ion , magnetic field , amplitude , resonance (particle physics) , atomic physics , cyclotron , acceleration , computational physics , classical mechanics , optics , quantum mechanics
We investigate a subharmonic‐resonant interaction between ions and magnetohydrodynamic waves propagating perpendicular to the background magnetic field, B o . This interaction occurs at frequencies which are subharmonics of the cyclotron frequency of ions (Ω i / n , where n is an integer, 2,3,4,...). We have found that this interaction becomes quite effective if the wave magnetic field δ B exceeds ∼10% of B o . Further, when δ B exceeds ∼50% of B o , ions have stochastic orbits in the wave and are accelerated with quite high efficiency. This subharmonic resonant interaction can play quite significant roles in the ion heating/acceleration processes in space plasmas, where large amplitude waves (δ B / B o ≳ 0.1) are not unusual. Possible observational features of the subharmonic resonance which we suggest are: (1) “absorption lines” in the broad background spectrum of compressible geomagnetic pulsations, and (2) enhancement of energetic ion fluxes relating to the large fluctuation of the magnetic field magnitude.