Remote sensing the magnetosheath by the spin modulation of terrestrial continuum radiation

Abstract

Using the Plasma Wave Instrument (PWI) data from the GEOTAIL satellite, we show that the angular intensity distribution of the Continuum Radiation (CR) received in the magnetotail regions changes from isotropic to anisotropic above a specific frequency. The transition frequency where this change occurs is primarily controlled by the upstream solar wind plasma frequency measured with IMP 8 satellite. We interpret the transition as evidence of the magnetosheath cavity trapping of terrestrial radiation. The transition frequency, strongly associated with the electron density in the tail bow shock regions, can be used as a new approach of remote sensing the global scale magnetosheath dynamics. Two preliminary case studies reveal the complex nonlinear responses of the tail magnetosheath to the steady and the transient solar wind variations. The 0–3 hour time delay of the variation in the transition frequency (corresponding to the magnetosheath electron density) relative to the upstream solar wind density variation may suggest that the magnetosheath plasma relaxes at the local Alfven speed, rather than the solar wind convection speed.