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Detailed Reference Information |
Winningham, J.D., Decker, D.T., Kozyra, J.U., Nagy, A.F. and Jasperse, J.R. (1989). Energetic (>60 eV) atmospheric photoelectrons. Journal of Geophysical Research 94: doi: 10.1029/89JA01167. issn: 0148-0227. |
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Data from the low altitude plasma instrument (LAPI) on Dynamics Explorer 2 document a population of high-energy (up to 800 eV) atmospheric photoelectrons that has not been reported in the published literature. The source of these photoelectrons is postulated to be the soft X ray portion of the whole Sun spectrum. This conclusion is supported by (1) sunrise-sunset characteristics that track those of the classical (<60 eV) EUV-produced photoelectrons and (2) theoretical results from two models that incorporate the soft X ray portion of the solar spectrum. The models include K shell ionization effects and predict peaks in the photoelectron spectrum due to Auger electrons emitted from oxygen and nitrogen. The peak for nitrogen is observed as predicted, but the peak for oxygen is barely observable. Excellent quantitative agreement is achieved between theory and experiment by using reasonable adjustments to the few published soft X ray spectra based on solar activity. The upflowing energetic photoelectrons provide a heretofore unknown source of electrons to the magnetosphere. They occur whenever and wherever the Sun is up, that is, at all invariant latitudes. Their density is low, but they are steady and ubiquitous. If scattering and trapping occur on closed field lines, then these photoelectrons could contribute as a significant particle source and thus represent a new facet of magnetosphere-ionosphere coupling. |
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BACKGROUND DATA FILES |
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Abstract |
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Keywords
Magnetospheric Physics, Energetic particles, precipitating |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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