1. Thermospheric Response to Transient Joule Heating and Solar-Flare Radiation Yanshi Huang, University of Texas at Arlington Arthur D. Richmond, NCAR High Altitude Observatory Yue Deng, University of Texas at Arlington Philip C. Chamberlin, NASA GFSC Solar Physics Laboratory Liying Qian, NCAR High Altitude Observatory Stanley C. Solomon, NCAR High Altitude Observatory Raymond G. Roble, NCAR High Altitude Observatory

2. Percentage Changes Heat and temperature perturbations are normalized to 1 at z=z 0, t=0.    (z 0 )c p H 2   c p T’

3. Globally Integrated Joule Heating Per Scale Height TIEGCM Simulation Conditions: Equinox Auroral Hemispheric Power = 20 GW Cross-polar-cap Potential = 50 kV F 10.7 = 200 F 10.7 = 70 GW (smin/smax)

4. Huang, Y., A.D. Richmond, Y. Deng, and R. Roble (2012), Height distribution of Joule heating and its influence on the thermosphere, J. Geophys. Res., 117, A08334, doi:10.1029/2012JA017885.

5. Altitude of unit optical depth vs. wavelength 0 40 80 120 160 200 240 280 320 (nm) 0-14 25-105 X-ray EUV 122-175 S-R

6. FISM

9. Conclusions Thermospheric temperature and density respond more rapidly and strongly to heat deposited at high altitudes than low altitudes. At solar maximum, the 400 km density response to F-region Joule heating on long time scales (~day) dominates over the response to E- region Joule heating. At solar minimum, the two are comparable. 0-14 nm flare energy can exceed that for 25-105 nm, but 25-105 nm has a much greater effect on 400 km thermospheric density. Flares also enhance high-latitude Joule heating through increases in electron density and, to a lesser extent, changes in neutral density. 122-175 nm flare radiation has a small but long-lasting impact on the thermosphere.