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

Abstract

[1] 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 dailyaveraged 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.

Impact of different energies of precipitating particles on NOx generation in the middle and upper atmosphere during geomagnetic storms

“…Since then several studies have shown good correlation between satellite observations of thermospheric NO concentration and various indicators of auroral electron precipitation (e.g., Petrinec et al, 2003). A significant fraction of large geomagnetic storms are associated with relativistic electron population increases in the outer radiation belt and the slot region.…”

Response of the Martian thermosphere/ionosphere to enhanced fluxes of solar soft X rays

“…The maximum densities at low latitudes were observed near 110 km. The large densities at high latitudes are assumed to be produced by auroral energetic (∼1–10 keV) electron precipitation [e.g., Gérard and Barth , 1977; Gérard et al , 1984; Barth et al , 2003; Petrinec et al , 2003]. Cleary [1986] developed a photochemical model of the NO densities in which variations in the EUV fluxes did not reproduce the observed low latitude NO density variations.…”

Energetic electron precipitation and the NO abundance in the upper atmosphere: A direct comparison during a geomagnetic storm

“…The study spanned over 3 years of data and the two data sets consisted of daily averages. Petrinec et al [2003] found a rather modest correlation between the measurements, indicating that 20–40% of the variation in the high‐latitude thermospheric nitric oxide was caused by the electron precipitation. The correlation was 0.57 when the NO observations were delayed one day with respect to the X‐ray measurements.…”

“…When also considering the seasonal effects on the NO density, the correlation coefficient increased from 0.57 to 0.63. However, Petrinec et al [2003] stressed the difficulties of doing a statistical comparison, when the timescales change significantly with observational circumstances and with altitude.…”