Seasonal Comparisons of Storm/Quiet Ratios Using TIMED/SABER NO+(v) VER Measurements and ISR Electron Densities at E-Region Altitudes

The TIMED/SABER instrument is a multi-channel radiometer that measures limb emission in the MLTI region. At night, 4.3um emission is used to estimate NO+(v) Volume Emission Rates (VER) at E-region altitudes. NO+(v) VER can be derived by removing the background CO2(nu3)4.3 um radiance contribution using SABER-based non-LTE radiation transfer models, and by performing a standard Abel inversion on the residual radiance. SABER observations show that NO+(v) VER is significantly enhanced during magnetic storms in accordance with increased ionization of the neutral atmosphere by auroral electron precipitation, followed by vibrational excitation of NO+ (i.e., NO+(v)) from fast exothermic ion-neutral reactions, and prompt infrared emission at 4.3 um. Due to charge neutrality, the NO+(v) VER enhancements are highly correlated with electron density enhancements, as observed for example by Incoherent Scatter Radar (ISR). In order to characterize the response of the storm-time E-region from both TIMED/SABER and ISR measurements, a Storm/Quiet ratio (SQR) parameter is defined as a function of altitude. For TIMED/SABER, the SQR is the ratio of storm-to-quiet NO+(v) VER. Similarly, SQR is the storm- to-quiet ratio of electron densities for ISR. In this work, we compare TIMED/SABER and ISR SQR values for different magnetic storm events seasonally distributed. Preliminary results indicate a good correlation between TIMED/SABER and ISR SQR values particularly between 100 to 120 km. SQR values are intended to be used as a correction factor to be included in an empirical storm-time correction to the International Reference Ionosphere model at E-region altitudes.