Large-scale observations of a subauroral polarization stream by midlatitude SuperDARN radars: Instantaneous longitudinal velocity variations

L. B.N. Clausen, J. B.H. Baker, J. M. Ruohoniemi, R. A. Greenwald, E. G. Thomas, S. G. Shepherd, E. R. Talaat, W. A. Bristow, Y. Zheng, A. J. Coster, S. Sazykin

Research output: Contribution to journalArticlepeer-review

Abstract

We present simultaneous measurements of flow velocities inside a subauroral polarization stream (SAPS) made by six midlatitude high-frequency SuperDARN radars. The instantaneous observations cover three hours of universal time and six hours of magnetic local time (MLT). From velocity variations across the field-of-view of the radars we infer the local 2D flow direction at three different longitudes. We find that the local flow direction inside the SAPS channel is remarkably constant over the course of the event. The flow speed, however, shows significant temporal and spatial variations. After correcting for the radar look direction we are able to accurately determine the dependence of the SAPS velocity on magnetic local time. We find that the SAPS velocity variation with magnetic local time is best described by an exponential function. The average velocity at 00 MLT was 1.2km/s and it decreased with a spatial e-folding scale of two hours of MLT toward the dawn sector. We speculate that the longitudinal distribution of pressure gradients in the ring current is responsible for this dependence and find these observations in good agreement with results from ring current models. Using TEC measurements we find that the high westward velocities of the SAPS are - as expected - located in a region of low TEC values, indicating low ionospheric conductivities.

Original languageEnglish (US)
Article numberA05306
JournalJournal of Geophysical Research: Space Physics
Volume117
Issue number5
DOIs
StatePublished - 2012

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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