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Dawn- Dusk Auroral Oval Oscillations Associated with High- Speed Solar WindWe report evidence of global-scale auroral oval oscillations in the millihertz range, using global auroral images acquired from the Ultraviolet Imager on board the decommissioned Polar satellite and concurrent solar wind measurements. On the basis of two events (15 January 1999 and 6 January 2000) studied, it is found that (1) quasi-periodic auroral oval oscillations (approximately 3 megahertz) can occur when solar wind speeds are high at northward or southward interplanetary magnetic field turning, (2) the oscillation amplitudes range from a few to more than 10 degrees in latitudes, (3) the oscillation frequency is the same for each event irrespective of local time and without any azimuthal phase shift (i.e., propagation), (4) the auroral oscillations occur in phase within both the dawn and dusk sectors but 180 degrees out of phase between the dawn and dusk sectors, and (5) no micropulsations on the ground match the auroral oscillation periods. While solar wind conditions favor the growth of the Kelvin-Helmholtz (K-H) instability on the magnetopause as often suggested, the observed wave characteristics are not consistent with predictions for K-H waves. The in-phase and out-of-phase features found in the dawn-dusk auroral oval oscillations suggest that wiggling motions of the magnetotail associated with fast solar winds might be the direct cause of the global-scale millihertz auroral oval oscillations. Plain Language Summary: We utilize global auroral image data to infer the motion of the magnetosphere and show, for the first time, the entire magnetospheric tail can move east-west in harmony like a windsock flapping in wind. The characteristic period of the flapping motion may be a major source of global long-period ULF (Ultra Low Frequency) waves, adding an extra source of the global mode ULF waves.
Document ID
20180002925
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Liou, Kan (Johns Hopkins Univ. Laurel, MD, United States)
Sibeck, David G. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
May 16, 2018
Publication Date
January 11, 2018
Publication Information
Publication: Journal of Geophysical Research-Space Physics
Volume: 123
Issue: 1
ISSN: 2169-9380
Subject Category
Geophysics
Report/Patent Number
GSFC-E-DAA-TN55710
Funding Number(s)
CONTRACT_GRANT: NNX14AF83G
WBS: WBS 960804.01.01.01
Distribution Limits
Public
Copyright
Other