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Possible evidence of virtual resonance in the dayside magnetosphere

Research output: Contribution to journalJournal article


  • Kazue Takahashi
  • David Berube
  • Dong-Hun Lee
  • Jerry Goldstein
  • Howard J. Singer
  • Farideh Honary
  • Mark B. Moldwin
<mark>Journal publication date</mark>8/05/2009
<mark>Journal</mark>Journal of Geophysical Research
Issue numberA05206
Number of pages11
Pages (from-to)1-11
<mark>Original language</mark>English


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.

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Copyright (2009) American Geophysical Union. Further reproduction or electronic distribution is not permitted