The Response of Thermospheric Nitric Oxide to the Geomagnetic Storm of April 2002

The presence of nitric oxide in the lower thermosphere is important for several reasons. NO plays a strong role in the thermospheric energy balance as it emits efficiently in the infrared, it is the terminal ion in the lower ionosphere and, if transported to lower altitudes, will catalytically destroy ozone. NO is primarily produced through the reaction of excited atomic nitrogen with molecular oxygen. One of the primary loss mechanisms of NO is photodissociation by solar ultraviolet irradiance. In order to produce the excited atomic nitrogen atom, the strong N2 molecular bond must be broken. It has been shown that at high latitudes, auroral electrons and the energetic secondary electrons provide the source of energy that leads to the large amounts of NO that are observed. The Student Nitric Oxide Explorer (SNOE) satellite has been observing NO in the thermosphere daily since February of 1998. Global observations of the abundance of NO were made throughout the period of the large geomagnetic storm that occurred April 16-20 of 2002. Large increases in NO abundance were observed during the storm. Auroral production of the NO is demonstrated by the distribution with magnetic latitude. Equatorward enhancement of NO was observed and suggests transport by meridional winds. Because the NO molecule has a lifetime of about one day, a high latitude observation of NO provides an indication of the integrated auroral energy deposition over the previous day. In this talk we will present the NO observations during the time period of the storm. We will also compare the observations to results from the ASPEN version of the TIME-GCM model now in use at SWRI.