Electromagnetic waves on ion gyro-radii scales across the magnetopause

Abstract

This report presents the first study of the global distribution and properties of kinetic scale electromagnetic waves on the Earth's magnetopause. From a statistical study using THEMIS fields observations over a frequency range from 0.01-2 Hz, we find waves on scales of the order of ion gyro-radii at all magnetic local times surveyed (4-20 MLT). The spectral energy densities (ε) within these waves across the magnetopause are larger on the dawn (4-12 MLT) than duskside (12-20 MLT) irrespective of the direction of the magnetosheath magnetic field B Z-sheath component. Furthermore, these observations reveal that ε is magnetic shear dependent with large enhancements for shear angle >60. The similarity between dawn-dusk asymmetry in ε we observe and reported distribution of magnetosheath ions in the magnetosphere suggest that gyro-radii scale magnetic field structures/waves may facilitate a significant fraction of cross magnetopause plasma transport. Copyright © 2011 by the American Geophysical Union.