Abstract
JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 114,
A05206,
11 PP., 2009
doi:10.1029/2008JA013898
Possible evidence of virtual resonance in the dayside magnetosphere
Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA
Department of Physics and Engineering Physics, Loyola Marymount University, Los Angeles, California, USA
Department of Astronomy and Space Science, Kyung Hee University, Yongin, South Korea
Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas, USA
NOAA/National Weather Service, National Centers for Environmental Prediction, Space Weather Prediction Center, Boulder, Colorado, USA
Department of Communications Systems, InfoLab21, Lancaster University, Lancaster, UK
Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California, USA
On day 108, 2001, the Sub-Auroral Magnetometer Network (SAMNET) and Magnetometers along the Eastern Atlantic Seaboard for Undergraduate Research and Education (MEASURE) magnetometer arrays detected dayside magnetic pulsations at a common frequency of ∼15 mHz at all locations below L = 4. This global pulsation event was associated with alignment of the interplanetary magnetic field with the Sun-Earth axis, a condition known to generate ultralow-frequency (ULF) waves in front of the bow shock. The event occurred during the early recovery phase of a geomagnetic storm. Magnetic field measured by the GOES 8 geostationary satellite on the dayside indicated elevated broadband (7–80 mHz) ULF power in the compressional component without a strong peak at 15 mHz. These observations suggest that the global pulsations originated from a compressional magnetohydrodynamic eigenmode oscillation of the inner magnetosphere stimulated by a broadband external disturbance. The equatorial Alfvén velocity corresponding to the toroidal frequencies that were determined with the cross-phase analysis of SAMNET and MEASURE data showed a gradual decrease of the velocity with L without a clear signature of a plasmapause. The observed properties of the global pulsations are consistent with virtual resonance in the inner magnetosphere.
Received 7 November 2008; accepted 10 March 2009; published 8 May 2009.
Citation: (2009), Possible evidence of virtual resonance in the dayside magnetosphere, J. Geophys. Res., 114, A05206, doi:10.1029/2008JA013898.
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