Upper-atmosphere perturbations at subauroral latitudes during an intense geomagnetic storm

Neutral gas density data of molecular nitrogen N2 and atomic oxygen O between 310 km and 330 km altitude as obtained by the Dynamic Explorer 2 satellite and ground-based foF2 data with ionosondes were used to examine the response of the thermosphere-ionosphere system to the intense geomagnetic storm of September 5, 1982. A comparison of simultaneous measurements of gas composition and peak electron density was obtained. Increase of N2 concentration and concurrent decrease of O concentration is observed. The N2 variation is greater than the O variation. Both changes contribute to explain the reduction in ionization density. Delayed increases of ionization are attributed to particle precipitation rather than to ionization transport.