Storm-Time Behaviors of the Thermospheric O/N2 and NO Variations

The thermospheric O/N2 column density ratio and nitric oxide (NO) column density are extracted from the TIMED/GUVI spectrograph data under sunlit conditions. The coincident O/N2 ratio and NO column density maps during a few geomagnetic storms reveal two major features: (1) Storm-time O/N2 depletion and NO enhancement extend from high to mid and low latitudes. They are anti-correlated on a global scale, (2) the NO enhancement covers a wider longitude and latitude region than O/N2 depletion on a local scale. The similarity between O/N2 depletion and NO enhancement on global scale is due to storm-time equatorward meridional wind that brings both O/N2 depleted and NO enhanced air from high to low latitudes. The altitude dependence of the storm-time meridional wind, different peaks altitudes of the local O/N2 and NO variations, and long life time of NO (one day or longer) may explain the different behaviors of O/N2 and NO on a local scale.