Large-amplitude hydromagnetic waves in the inner magnetosheath

Abstract

We find that slow magnetoacoustic waves produce the magnetic field perturbations of the largest amplitude in the 0.01- to 0.1-Hz frequency range within the ‘highly disturbed’ magnetosheath. The frequencies quoted are frequencies seen by the satellite. Rotational Alfvén waves with periods of several minutes and longer are also detected on most orbits. The power spectrum of rotational waves usually rises much more steeply below 0.01 Hz than the power spectrum of magnetoacoustic waves. We conclude that the magnetoacoustic waves are produced or strongly amplified at the earth's bow shock or in the outer magnetosheath. The observed rotational waves may be produced beyond the bow shock and carried into the magnetosheath by the solar wind.