Nitrogen Dioxide Variations Caused by Penetration of Solar Protons into the High-Latitude Atmosphere

The results of spectroscopic measurements of the NO₂ total content during the solar proton event of the GLE (Ground Level Event) type on May 2, 1998, at the Murmansk (" = 64.5°) and Sodankyla (" = 63.7°) stations are presented. The vertical profiles of the nitrogen oxide (NO) distribution in the stratosphere according to the UARS satellite data during another GLE event on July 14, 2000, are also presented. It is shown that the high-energy solar protons penetrating into the atmosphere lead to a considerable increase in the nitrogen oxide concentration and the GLE on May 2, 1998, resulted in an increase of the NO₂ total content according to the ground-based observations at high latitudes. It is worth noting that no decrease of the total ozone content (TOC) was recorded during these proton events according to the ground-based measurements at high latitudes. The corresponding calculations of the nitrogen oxide changes during proton events based on the homogeneous photochemical theory are presented. The interrelation between all the quantities measured, as well as their relation to the calculated values, is considered. It is shown that a considerable increase of nitrogen oxides in the atmosphere does not always result in an ozone concentration depletion. The results presented indicate a need to provide simultaneous ground-based and satellite measurements of nitrogen oxides and ozone at high latitudes.