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Wave and ion evolution downstream of quasi-perpendicular bow shocksDistribution functions of ions heated in quasi-perpendicular bow shocks have a large perpendicular temperature anisotropy that provides free energy for the growth of Alfven ion cyclotron (AIC) waves and mirror waves. Both types of waves have been observed in the Earth's magnetosheath downstream of quasi-perpendicular shocks. We use a two-dimensional hybrid simulations to give a self-consistent description of the evolution of the wave spectra downstream of quasi-perpendicular shocks. Both mirror and AIC waves are identified in the simulated magnetosheath. They are generated at or near the shock front and convected away from it by the sheath plasma. Near the shock, the waves have a broad spectrum, but downstream of the shock, shorter-wavelength modes are heavily damped and only longer-wavelength modes persist. The characteristics of these surviving modes can be predicted with reasonable accuracy by linear kinetic theory appropriate for downstream conditions. We also follow the evolution of the ion distribution function. The shocked ions that provide the free energy for wave growth have a two-component distribution function. The halo is initially gyrophase-bunched and extremely anisotropic. Within a relatively short distance downstream of the shock (of the order of 10 ion inertial lengths), wave-particle interactions remove these features from the halo and reduce the anisotropy of the distribution to near-threshold levels for the mirror and AIC instabilities. A similar evolution has been observed for ions at the Earth's bow shock.
Document ID
19950047147
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Mckean, M. E.
(University of California, San Diego, La Jolla, CA United States)
Omidi, N.
(University of California, San Diego, La Jolla, CA United States)
Krauss-Varban, D.
(University of California, San Diego, La Jolla, CA United States)
Date Acquired
August 16, 2013
Publication Date
March 1, 1995
Publication Information
Publication: Journal of Geophysical Research
Volume: 100
Issue: A3
ISSN: 0148-0227
Subject Category
Geophysics
Accession Number
95A78746
Funding Number(s)
CONTRACT_GRANT: NAG5-1492
Distribution Limits
Public
Copyright
Other

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