The northern auroral region as observed in nitric oxide

Abstract

The distribution of thermospheric nitric oxide in the northern polar region has been measured from the Student Nitric Oxide Explorer (SNOE). A polar image of a one-year average at 106 km shows the maximum density lies between 60° and 70° N geomagnetic latitude. The density around this auroral oval varies as a function of longitude with the larger densities occurring at western geomagnetic longitudes. A polar image of a second year of observations demonstrates the same latitudinal longitudinal density distribution indicating that the asymmetry is a persistent property of the auroral region. For a period of high geomagnetic activity, the nitric oxide observations indicate that the flux of precipitating electrons at 90° W geomagnetic longitude was 75% larger than the flux at 90° E geomagnetic longitude. We suggest that this asymmetry is caused by the longitudinal variation in the magnetic field strength around the auroral oval.