The dynamic cusp at low altitudes: a case study utilizing Viking,DMSP-F7, and Sondrestrom incoherent scatter radar observations |
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| Authors: | J Watermann O de la Beaujardière D Lummerzheim J Woch P T Newell T A Potemra F J Rich M Shapshak |
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| Institution: | (1) Geoscience and Engineering Center, SRI International, Menlo Park, CA 94025, USA;(2) Geophysical Institute, University of Alaska, Fairbanks, AK 99701, USA;(3) Swedish Institute of Space Physics, S-98128 Kiruna, Sweden;(4) Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723, USA;(5) Phillips Laboratory, Hanscom Air Force Base, Bedford, MA, 01731, USA;(6) Alfvén Laboratory, Royal Institute of Technology, S-10044 Stockholm, Sweden;(7) NATO SACLANT Undersea Research Centre, I-19138 La Spezia, Italy;(8) Max-Planck-Institut für Aeronomie, D-37189 Katlenburg-Lindau, Germany |
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| Abstract: | Coincident multi-instrument magnetospheric and ionospheric observations have made it possible to determine the position of the ionospheric footprint of the magnetospheric cusp and to monitor its evolution over time. The data used include charged particle and magnetic field measurements from the Earth-orbiting Viking and DMSP-F7 satellites, electric field measurements from Viking, interplanetary magnetic field and plasma data from IMP-8, and Sondrestrom incoherent scatter radar observations of the ionospheric plasma density, temperature, and convection. Viking detected cusp precipitation poleward of 75.5○ invariant latitude. The ionospheric response to the observed electron precipitation was simulated using an auroral model. It predicts enhanced plasma density and elevated electron temperature in the upper E- and F-regions. Sondrestrom radar observations are in agreement with the predictions. The radar detected a cusp signature on each of five consecutive antenna elevation scans covering 1.2 h local time. The cusp appeared to be about 2○ invariant latitude wide, and its ionospheric footprint shifted equatorward by nearly 2○ during this time, possibly influenced by an overall decrease in the IMF Bz component. The radar plasma drift data and the Viking magnetic and electric field data suggest that the cusp was associated with a continuous, rather than a patchy, merging between the IMF and the geomagnetic field. |
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