Abstract

Geomagnetic storms release large amounts of energy on Earth's upper atmosphere at high latitudes that result in the heating and upward expansion of the neutral gas. During geomagnetic storms driven by interplanetary coronal mass ejections (ICMEs), neutral mass density heating and cooling times are shorter for stronger storms and longer for weaker storms. The start time influx of energy into Earth's upper atmosphere allows for the enhanced production of nitric oxide (NO) at high latitudes, which in turn cools the thermosphere by radiating away excess energy. As a result, greater NO production results in quicker thermospheric cooling. While the production of NO on a global scale has been linked to the storm cycle, the spatiotemporal evolution of NO with respect to the storm onset and storm strength must also be understood to improve predictions of the storm evolution cycle and their impact on low-Earth orbit satellites. In this study, we investigate the effects of a particular ICME-driven storm on the production of NO at high latitudes and associated local time asymmetries. We compare NO measurements from the Thermosphere, Ionosphere, Mesosphere Dynamics (TIMED) spacecraft to neutral mass density measurements from the Challenging Minisatellite Payload spacecraft and find that the impact of the shock prior to the storm, in addition to the onset of the storm itself, is responsible for an increase in NO production. We also observe a dawn-dusk asymmetry in high-latitude NO production and identify solar wind geometry and internal processes as potential drivers for this asymmetry.