Ion-Acoustic Waves in a Quasi-Perpendicular Earth's Bow Shock

We present analysis of electrostatic waves around the ramp of a quasi-perpendicular Earth's bow shock observed by the Magnetospheric Multiscale spacecraft. The electrostatic waves have amplitudes up to 800 mV/m, which is the largest value ever reported in the Earth's bow shock. In contrast to previous studies, the electrostatic waves have large amplitudes of the electrostatic potential, up to 20 V or 20% of local electron temperature. The wavelengths are from 150 m to 3 km, that is from 15 to 300 Debye lengths and typically from 0.4 to 1.5 thermal electron gyroradii. Importantly, these waves can propagate not only quasi-parallel or oblique, but also almost perpendicular to local magnetic field. The electrostatic waves are interpreted in terms of ion-acoustic waves, although the presence of electron cyclotron harmonic waves cannot be entirely ruled out. These results suggest that electrostatic waves may strongly affect the dynamics of electrons in collisionless shocks.

Automated summary

This study presents an analysis of electrostatic waves observed near the quasi-perpendicular Earth's bow shock by the Magnetospheric Multiscale spacecraft. The analysis reveals that these electrostatic waves have large amplitudes and can propagate almost perpendicular to the local magnetic field. The results suggest that these waves may strongly affect the dynamics of electrons in collisionless shocks.