Global observations of ring current dynamics during corotating interaction region-driven geomagnetic storms in 2008

Abstract

We examine the evolution of the ring current during the main and early recovery phases of three geomagnetic storms driven by corotating interaction regions. The equatorial energy density profiles of 5-30 keV ions are calculated from deconvolved energetic neutral atom images from the Two Wide-Angle Imaging Neutral-Atom Spectrometers mission. The energy density in the ring current is enhanced by almost a factor of 2 and stretches from postmidnight to dusk immediately following injections identified by in situ measurements. The energy density then drops back to preinjection levels within 1-2 h. We also find that there are often two peaks in the energy density following the injection, one at midnight and one close to dusk. We present the spectra for these peaks to show they contain different ion populations. The asymmetry of the ring current observed is found to agree with previous in situ and simulation studies.