Inner magnetosphere convection and magnetotail structure of hot ions imaged by ENA during a HSS‐driven storm

Abstract

The remotely measured increase in plasma sheet ion temperatures during high speed stream‐driven storms is greater than that of ICME‐driven storms. These hot ions are convected to the inner magnetosphere where they drive the ring current. On 22 July 2009, a high speed stream yielded a moderate (minimum Dst of −79 nT) storm, one of the largest that occurred during the extended solar minimum between January 2007 and September 2010. We present measurements obtained with an energetic neutral atom (ENA) imager of the TWINS mission during the main phase of the storm. Ion temperatures calculated from the ENA measurements show storm‐time increase in ion temperature and a subsequent convection of hot ions into the inner magnetosphere. In the magnetotail, a region of hot ions near local midnight is observed that may be associated with substorm‐related bursty bulk flows.