Global view of inner magnetosphere composition during storm time

Abstract

Plasma dynamics in the inner magnetosphere are greatly affected by variations in the ion composition. The ratio of hydrogen to oxygen has been shown to be highly dependent on geomagnetic activity. To investigate this dependence, we examine the timing of the injection and subsequent evolution of O+ in the ring current during the storm of 6 August 2011 as observed by Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) instruments. To help interpret magnetospheric evolution using the global O Energetic Neutral Atom (ENA) emission measured by TWINS, we have employed a multidomain modeling of the global magnetosphere using the Space Weather Modeling Framework. TWINS Energetic Neutral Atom (ENA) imagers have the capability to distinguish between H and O emission and thus the major ion constituents of the ring current. Global composition measurements from TWINS spacecraft show intensifications of the oxygen ENA emission and thus an increase in the transport of ionospheric oxygen into the ring current that occur during the main phase of the storm. Both the observations and the simulation suggests that the peak in O ENA emission is correlated with the substorm injections that occurred during this time. The model also shows a very dynamic magnetosphere that allows for loss of oxygen from the Earth-magnetosphere system through plasmoids capable of transporting oxygen down the tail throughout the magnetic storm. This can possibly be a predominant pathway for loss of oxygen from the magnetosphere. Key Points Initial TWINS observations of oxygen ENA. O ENA emission peak is correlated with the substorm injections. Loss of oxygen from magnetoshere through plasmoids transporting it tailward. © 2013 The Authors. Journal of Geophysical Research: Space Physics published by Wiley on behalf of the American Geophysical Union.