Interhemispheric differences in the HF radar signature of the cusp region: A review through the study of a case example

Abstract

This paper aims to provide a review of our understanding of the HF radar signatures of the cusp and transient magnetopause reconnection phenomena through the study of a case example. Two Super DARN radars observe the conjugate cusp regions during an interval of southward IMF. These observations allow us to determine several parameters relating to the electrodynamics of the magnetopause reconnection process, including the mean reconnection voltage and the reconnection electric fields and X-line lengths in the two hemispheres. In addition, we identify several differences between the radar and flow signatures observed in the two hemispheres, specifically that flux transfer event signatures are observed in the Northern Hemisphere but not the Southern Hemisphere, and that the azimuthal component of the flow excited by reconnection is much greater in the Southern Hemisphere than in the Northern Hemisphere. We finish our discussion by identifying remaining questions regarding the interpretation of HF radar observations of the cusp