The upper atmosphere as a regulator of subauroral red arcs |
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| Authors: | S ChandraEJ Maier |
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| Institution: | Thermosphere & Exosphere Branch, Code 621, Laboratory for Planetary Atmospheres, Goddard Space Flight Center, Greenbelt, Maryland 20771 U.S.A.; Max-Planck-Institut fur Aeronomie, 3411 Lindau, Harz, West Germany |
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| Abstract: | The mechanisms for producing a subauroral red arc (SARARC) are studied by solving a system of basic ionospheric and atmospheric equations. It is shown that many of the observed features of a SARARC can be explained within the framework of the two processes generally responsible for the ionospheric behavior during a magnetic storm: these are (1) energy conduction from the magnetosphere to the ionosphere and (2) the changes in neutral composition of the lower atmosphere caused by the increase in turbulent mixing. Both the processes trigger a complex chain of events which ultimately results in the redistribution of both the charged and neutral particles, an increase in the electron, ion, and neutral temperatures, and a decrease in the electron density in the altitude region near the F2 peak. It is shown that both the occurrence and the emission intensity of a SARARC are regulated by the neutral atmosphere, even though conduction of the thermal energy from the magnetosphere to the ionosphere provides the excitation energy fo the optical remission. Recent satellite measurements of the ionospheric parameters have confirmed the validity of these findings and have provided grounds for rejecting several other theories which have been proposed in the literature. |
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