Relationships between precipitating auroral zone electrons and lower thermospheric nitric oxide densities: 1998-2000

Data acquired using the Student Nitric Oxide Explorer (SNOE) spacecraft dur ing the years 1998-2000 are presented for nitric oxide (NO) measured at alt itudes between 90 and 170 km. These data are compared with energetic electr on fluxes (E > 25 keV) measured concurrently using a large-area microchanne l plate sensor system (Low-Energy Ion Composition Analyzer) (LICA) on board the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) spacec raft. Three geomagnetic storm intervals (in May 1998, September 1998, and O ctober 1998) are examined specifically to determine altitude and latitude v ariations of NO production as it compares to energetic electron precipitati on. A broader statistical analysis is then carried out using daily averages of peak NO densities (at 106 km altitudes) and electron intensities measur ed by SAMPEX. Northern and Southern Hemisphere data are treated separately within the magnetic latitude bands 60 degrees -70 degrees north and south. We find correlation coefficients of 0.56 (north) and 0.73 (south) for NO de nsity versus SAMPEX electron count rates using two complete years of data. We also use the National Oceanic and Atmospheric Administration (NOAA) "hem ispherical power index" to compare with SAMPEX and with SNOE measurements. Correlation coefficients of similar to0.6 are found among all the daily-ave raged quantities, suggesting that perhaps 30-40% of the variance in NO dens ity can be accounted for by the particle measurements used. An analysis and adjustment of NO densities to account for seasonal effects increases the N O correlations with particle intensities to greater than or similar to0.7.