High-Resolution Observations of Subauroral Polarization Stream-Related Field Structures During a Geomagnetic Storm Using Passive Radar

Abstract

In observations made with the Manastash Ridge Radar (MRR, the University of Washington's passive, VHF coherent radar) during July 2004, we detected a large-scale wavelike structure (in latitude and/or time) that propagated through the field of view. The amplitude and period of these equatorward-moving oscillations in backscatter intensity closely resemble those reported by the Millstone Hill Atmospheric Science Group [Foster et al., 2004] in their studies of spatial and temporal variations in the subauroral polarization stream (SAPS) electric field. We present supporting evidence from Defense Meteorological Satellite Program (DMSP) satellite measurements to show that a SAPS channel was present in the MRR field of view during the time in question. By treating individual backscattering irregularities (present due to ionospheric two-stream instabilities) as tracers for electric field structure within the larger and longer-lived SAPS channel, we find quasi-periodic oscillations in the field structure within the channel as well as an equatorward motion of the entire SAPS structure.