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Importance of the Height Distribution of Joule Heating for Thermospheric Density Arthur D. Richmond and Astrid Maute NCAR High Altitude Observatory. . b. Field-Aligned Poynting Flux, IMF B z = -5 nT, B y = 0. S p|| . b. . b. Summer. 104 GW. 73 GW. 177 GW. 10. 10. 20. mW/m 2. - PowerPoint PPT Presentation
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Importance of the Height Distribution of Joule Heating for Thermospheric Density
Arthur D. Richmond and Astrid MauteNCAR High Altitude Observatory
Field-Aligned Poynting Flux, IMF Bz = -5 nT, By = 0
Summer
Winter
.b .b Sp||.b
104 GW
56 GW
177 GW
120 GW64 GW
73 GW
10
mW
/m2
mW
/m2
mW
/m2
mW
/m2
mW
/m2
mW
/m2
10 10
10
-10 -10
-10 -10
-10
-10
20
20
TIE-GCM Experiments
Base case: - Steady-state, Day number = 80- F10.7 = 150 - Polar-cap Potential = 45 kV- Hemispheric Power of auroral particles = 16 GW
Test cases:- 9 GW additional neutral heating in each hemisphere - proportional to vi
2 in latitude and longitude- turned on during UT hours 1-6 on Day 1, then off
(a) High Heat at 270 km ± 1 scale height(b) Low Heat at 120 km ± 1 scale height
High Heat is centered 5 scale heights above Low Heat (e5 = 148)
Height-Integrated Additional Heating
mW
/m2
X
700 W
0.56
0.28
0.06
6 UT 12 UT 18 UTTemperature Difference at -700 Longitude
High Heat, 3 K contour interval
Low Heat, 1K contour interval
6 UT 12 UT 18 UTDensity Difference (%) at -700 Longitude
High Heat, 3% contour interval
Low Heat, 1% contour interval
High Heat
Low Heat
Global Mean
Global Mean
KK
KKTemperature Difference at 400 km
700 W
700 W
Conclusions- F-region Joule heating, though only a small fraction of total Joule heating, produces a strong, fast (hours) temperature and density response at 400 km that decays rapidly.
- F-region Joule heating depends on highly variable conductivity. It may be much more important with intense soft particle precipitation and at solar maximum.
- E-region heating produces a slow (~1 day) response at 400 km that decays slowly. It is important for long-term variations of temperature and density.
- Poynting flux and geomagnetic indices are inadequate for determining high-altitude Joule heating. Observations and modeling of polar F-region electron densities, in relation to electric fields, are needed.
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