Thermospheric Response to Transient Joule Heating and Solar-Flare Radiation Yanshi Huang, University...

Thermospheric Response to Transient Joule Heating and Solar-Flare Radiation

Yanshi Huang, University of Texas at ArlingtonArthur D. Richmond, NCAR High Altitude Observatory

Yue Deng, University of Texas at ArlingtonPhilip C. Chamberlin, NASA GFSC Solar Physics Laboratory

Liying Qian, NCAR High Altitude ObservatoryStanley C. Solomon, NCAR High Altitude ObservatoryRaymond G. Roble, NCAR High Altitude Observatory

Percentage Changes

Heat and temperature perturbations are normalized to 1 at z=z0, t=0.

t0 = r(z0)cpH2/k

= rcpT’

Globally Integrated Joule Heating Per Scale Height

TIEGCM Simulation Conditions:EquinoxAuroral Hemispheric Power = 20 GWCross-polar-cap Potential = 50 kV

F10.7 = 200

F10.7 = 70

GW

(smin/smax)

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.

Altitude of unit optical depth vs. wavelength

0 40 80 120 160 200 240 280 320(nm)

0-14 25-105X-ray EUV

122-175S-R

FISM

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.