HR: 1400h
AN: SM53A-07    [Abstracts]
TI: Space Technology 5 Observations of Short-Period ULF Waves: Temporal and Spatial Patterns
AU: * Westerman, A
EM:
AF: Department of Physics, Augsburg College, Minneapolis, MN 55454, United States
AU: Otto, N
EM:
AF: Department of Physics, Augsburg College, Minneapolis, MN 55454, United States
AU: Engebretson, M
EM: engebret@augsburg.edu
AF: Department of Physics, Augsburg College, Minneapolis, MN 55454, United States
AU: Slavin, J
EM:
AF: Heliophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, United States
AU: Le, G
EM:
AF: Heliophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, United States
AU: Strangeway, R
EM:
AF: IGPP, UCLA, Los Angeles, CA 90024, United States
AB: The three microsatellites that comprise the Space Technology 5 (ST5) mission were launched into a dawn-dusk, 300 x 4500 km sun-synchronous orbit in a "pearls-on-a-string" configuration, with spacings ranging from >5000 km down to under 50 km. Fluxgate magnetometers on board each spacecraft collected vector magnetic field data from March 26 through June 30, 2006. In this study we present the first results of a survey of ULF waves in the Pc 1-2 frequency range, with a total of 105 events, recorded by these spacecraft. Waves in the middle magnetosphere (L from 4 to 7) were observed to have a nearly uniform diurnal occurrence rate. At higher latitudes (L > 7) occurrence was maximum in the dawn-noon sector, consistent with stimulation by magnetospheric compressions. Only five wave events were observed at L < 4. The temporal occurrence distribution roughly followed the occurrence of Pc 1-2 activity recorded at Halley, Antarctica (L = 4.5), in that the number and intensity of events was increased during magnetospheric compressions, during the recovery phase of magnetic storms, and during one extended interval of disturbed but only modestly negative Dst. Somewhat surprisingly, only eight events were observed by all three spacecraft as they passed over similar L shells, and only 14 events, including two each on three days, were observed by two spacecraft. Nearly all of these events occurred during storm recovery. We interpret the lack of more multi-spacecraft observations as indicating the highly localized nature of regions in the magnetosphere that become unstable to electromagnetic ion cyclotron instabilities.
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
DE: 2784 Solar wind/magnetosphere interactions
DE: 2788 Magnetic storms and substorms (7954)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly