HR: 0800h
AN: SA51A-1124    [Abstracts]
TI: Joule Heating and Nitric Oxide in the Thermosphere
AU: Barth, C A
EM: charles.barth@lasp.colorado.edu
AF: LASP/Univ of Colorado, 1234 Innovation Drive, Boulder, CO 80303-7814 United States
AU: * Bailey, S M
EM: scott.bailey@gi.alaska.edu
AF: Geophys. Institute/Univ. of Alaska, 903 Koyukuk Dr., Fairbanks, AK 99775 United States
AU: Lu, G
EM: ganglu@ucar.edu
AF: HAO/NCAR, 3450 Mitchell Lane, Boulder, CO 80307 United States
AU: Baker, D N
EM: daniel.baker@lasp.colorado.edu
AF: LASP/Univ of Colorado, 1234 Innovation Drive, Boulder, CO 80303-7814 United States
AB: The density of nitric oxide at 150 km may be used as an indicator of Joule heating in the thermosphere. The chemical reaction between nitrogen atoms (ground state) and molecular oxygen that produces nitric oxide at this altitude is very sensitive to temperature. During a Joule heating event the temperature of the thermosphere increases by 50 to 100 K leading to an increase in the nitric oxide density by a factor of two. The density distribution of nitric oxide has been studied for a Joule heating event that occurred on September 25, 1998. The global distribution of nitric oxide density was measured from a limb-scanning instrument on the SNOE polar orbiting satellite. On September 22, electrons began to precipitate into the thermosphere causing an increase in the nitric oxide density at 110 km at auroral latitudes. On September 24, as the result of Joule heating the nitric oxide density at 150 km began to increase reaching a maximum on September 25. The increased nitric oxide density extended equatorward from auroral latitudes to 20 degrees latitude. The 150 km nitric oxide density decreased on September 26 and was back to normal levels by September 28. The electron precipitation reached its maximum on September 26 and continued through September 28. The comparison of the observed nitric oxide with model calculations of the altitude distribution of nitric oxide clearly showed the increased nitric oxide produced by Joule heating. The increased nitric oxide at 150 km was used as an indicator of Joule heating for a 935-day period from March 1998 to September 2000. Increased nitric oxide at 110 km was used as an indicator of electron precipitation for this same period. It was found that the seasonal behavior of Joule heating and electron precipitation differ, with electron precipitation events occurring more frequently during the winter seasons and Joule heating events occurring more frequently during the summer seasons.
DE: 0358 Thermosphere: energy deposition (3369)
DE: 2411 Electric fields (2712)
DE: 2427 Ionosphere/atmosphere interactions (0335)
DE: 2704 Auroral phenomena (2407)
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005