Large-scale structures in the Polar Rain

Abstract

We present two distinctive spatial structures (~140 and ~1000 km) in the polar rain electron energy fluxes observed by Defense Meteorological Satellite Program satellites. The 16 May 2005 event indicates that sources of the ~1000 km structures were not in the solar wind electrons. Statistical analysis of 239 events shows that the ~1000 km structures were associated with high solar wind speed and density while the ~140 km structures did not depend on solar wind conditions. The structures are about 5 and 0.7 RE when mapped to the magnetopause and comparable to the typical Kelvin-Helmholtz (KH) wavelengths (3-14 RE) and flux transfer event (FTE) sizes (~0.6-1.3 R E) on the magnetopause. Our calculations indicate that the KH waves are unstable under the high solar wind speed and density. The observations and calculations suggest that the ~1000 km and ~140 km structures are likely caused by the KH waves and FTE on the magnetopause. Key Points Two distinctive spatial structures (~140 and ~1000 km) in the polar rain Dependence of the ~1000 km structures on high solar wind speed and density KH waves and FTE cause the ~1000 and ~140 km structures in the polar rain ©2013. American Geophysical Union. All Rights Reserved.