Comparisons of thermospheric high‐latitude nitric oxide observations from SNOE and global auroral X‐ray bremsstrahlung observations from PIXIE

Abstract

Three years (March 1998 through March 2001) of nitric oxide (NO) observations in the Northern Hemispheric thermosphere (90–170 km) as made by the Student Nitric Oxide Explorer (SNOE) spacecraft are compared in a broad statistical analysis with the daily‐averaged northern auroral bremsstrahlung x‐ray observations, which are taken to be a good proxy for the population of precipitating energetic electrons. The latter are made by the Polar Ionospheric X‐ray Imaging Experiment (PIXIE) on board the NASA GGS Polar spacecraft. A modest correlation between these two data sets is found, indicating that about 20–40% of the variation in the number density of thermospheric nitric oxide at high latitudes is caused by variations in the precipitation of energetic particles from the magnetosphere into the auroral regions of the ionosphere. Time delays between the two data sets are examined in this study, as well as the altitude profile of the nitric oxide observations. Differences in the response and recovery times in the two data sets are also carefully considered along with hemispheric asymmetries as a function of season, leading to stronger correlations which are then discussed in terms of the properties of the data sets used.