Magnetosonic waves: Hydrodynamics vs kinetics
- Ben-Gurion Univ., Beer-Sheva (Israel). Dept. of Physics
Magnetosonic waves play an important role in the collisionless shock life. The shock front itself forms due to the magnetosonic wave steepening. Most of the turbulent energy in the shock front is in the low frequency waves, i.e. magnetosonic and Alfven waves and whistlers. Hydrodynamical description of magnetosonic waves works well when {beta} = 8{pi}nT/B{sup 2} {much_lt} 1, but produces incorrect results in the high {beta} cases. In particular, the dispersion of the oblique magnetosonic wave in low {beta} plasma is determined by the ion inertial length c/{omega}{sub pi} and is positive. In the high {beta} plasma the dispersion of the quasiperpendicular magnetosonic wave is determined by the ion gyroradius {rho}{sub i} = {upsilon}{sub T}/{Omega}{sub i}, and is negative. Wave observations at high {beta} shocks confirm the conclusion that kinetic approach is necessary to describe properly the magnetosonic wave features. Nonlinear wave equations for low-frequency waves, obtained from (semi)kinetic approach, also differ from those obtained from hydrodynamical equations. Although the main difference is in the strong dependence of the dispersive term on the plasma {beta}, the nonlinear interaction also becomes significantly {beta} dependent. This work is applicable to space plasmas.
- OSTI ID:
- 163167
- Report Number(s):
- CONF-950612--; ISBN 0-7803-2669-5
- Country of Publication:
- United States
- Language:
- English
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