Ion Temperature Maps of the Plasma Sheet During HSS-driven storms Calculated from TWINS ENA Measurements

While geomagnetic storms can be driven by interplanetary coronal mass ejections (ICMEs) and high speed streams (HSSs) in the solar wind, the magnetospheric response varies depending on the driver. For example, electron and ion temperatures measured at geosynchronous orbit increase during both types of storms, but the temperature increase is much larger during HSS-driven storms [Denton et al., 2006]. For HSS-driven storms, ion temperatures measured at geosynchronous orbit increase sharply at the time of convection onset and remain elevated for the duration of the HSS-driven event [Denton and Borovsky, 2008]. These hot ions are convected to the inner magnetosphere where they can drive the ring current. An injection of hot ions to the inner magnetosphere can be seen during the 22 July 2009 HSS-driven event in ion temperature maps calculated using energetic neutral atom (ENA) measurements provided by the TWINS dual-spacecraft mission. We will present these ion temperature maps along with those from additional HSS-driven events. The two TWINS spacecraft provide excellent spatial and temporal coverage for the study of ion heating during HSS-driven storms.