Electrodynamic response of the middle atmosphere to auroral pulsations |
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| Institution: | 1. Laboratory for Extraterrestrial Physics. NASA Goddard Space Flight Center. Greenbelt, MD 20771, U.S.A.;2. Department of Electrical Enginecring-CSSL, The Pennsylvania State University. University Park, PA 16802. U.S.A.;3. University of Denver. Denver, CO 80208. U.S.A.;1. School of Geodesy and Geomatics, Wuhan University, No. 129 Luoyu Road, Wuhan 430079, China;2. GNSS Research Center, Wuhan University, No. 129 Luoyu Road, Wuhan 430079, China;1. Space Physics Laboratory, Vikram Sarabhai Space Center, Trivandrum 695022, India;2. Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada;1. Mbarara University of Science and Technology, Department of Physics, Mbarara P. O. Box 1410, Uganda;2. Muni University, Department of Physics, Arua P.O. Box 725, Uganda;3. Swedish Institute of Space Physics, Uppsala, Sweden;4. South African National Space Agency, Hospital Street, Hermanus P. O. Box 32, South Africa;5. Rhodes University Makhanda, Department of Physics and Electronics, 6139, Eastern Cape, P. O. Box 6140, South Africa |
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| Abstract: | On the nights of 21 and 28 October 1987, two Nike Orion payloads (NASA 31.066 and 31.067) were launched from Andøya, Norway, as part of the MAC/EPSILON campaign, to study the effect of auroral energetics on the middle atmosphere. Each payload carried detectors to measure relativistic electrons from 0.1 to 1.0MeV in 12 differential energy channels, and bremsstrahlung X-rays from >5 to >80keV in 5 integral channels. In addition, instrumentation to measure bulk ion properties and electric fields was also carried by these and/or near simultaneous flights. Flight 31.066 was launched during the recovery phase of a moderate magnetic substorm, during relatively stable auroral conditions. Flight 31.067 was launched during highly active post-break-up conditions during which Pc 5 pulsations (> 150s period) were in progress. The energetic radiation of the first event was composed almost entirely of relativistic electrons below 200 keV with negligible contributions from bremsstrahlung X-rays, while the radiation of the second event was dominated by much softer electrons ( < 100 kcV), which produced high X-ray fluxes that exceeded the cosmic ray background as an ionizing source down to altitudes below 30 km. Simultaneous conductivity measurements during both events show consistency with the ionizing radiations, with the pulsation event producing free electrons down to 55 km. far below their expected altitude range during night-time. These comparisons are discussed to evaluate the impact of such events on the middle atmosphere. |
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