Low altitude observations of ENA from the ring current and from the proton oval

Observations of Energetic Neutral Atoms (ENAs) emitted from the proton aurora and from the equatorial ring current at tens to a few hundred of key during the Halloween 2003 storm are presented. From the proton oval a large number of ENAs are spread over the polar cap making a contribution to the ion outflow. From the Ring Current (RC) ENAs are spread in all directions. The Storm Time Equatorial Belt (STEB) consists of ENAs observed around the geomagnetic equator at low L-values. Their source is RC protons existing at larger L-values. The number of observed ENAs is directly dependent on the amount of ions (protons) present in the RC along the line of sight. Thus the time variations of the STEB enable us to monitor the behavior of the RC. Based on observations of the STEB at six different local times we discuss the RC injection region, the drift of RC-particles through the evening/afternoon sector into the morning sector and the RC decay time during the storm recovery phase. The MLT variation of the STEB gives information about the symmetry and asymmetry of the RC with no interference from other current systems. The revealed RC-symmetry and asymmetry complement magnetic ground observations. (C) 2012 Elsevier Ltd. All rights reserved.