2011 SuperDARN Workshop       

Phase coherence on open field lines associated with FLRs

A. Nedie, F. Fenrich and R. Rankin
University of Alberta, Edmonton, Alberta, Canada

abstract. A wide variety of waves occur in the magnetospheric regions of Earth excited by sources internal to the magnetosphere and external sources in the solar wind. Amongst them are the ULF waves whose direction of propagation is an important indicator of where the source mechanism might be located. For years, ULF field line resonances were known to cause oscillations in the F-region plasma flows, which are detected in SuperDARN?s measured line-of-sight Doppler velocities. In this talk, discernible FLR signatures at 0.8-mHz, extended azimuthally along the latitude contour and its associated source in the solar wind using simultaneous measurements from multiple HF radars will be presented. We characterize ULF observations with coordinated simultaneous HF radars, optical instrumentation, ground-based magnetometers and satellite-borne instrumentation. During the time interval of interest, Geotail was on an outbound pass from the dawn side magnetosheath into the upstream sola r wind region. In this talk, we present a completely new feature of phase coherence on open field lines at exactly the same resonant frequency. Equally important and new in this study is; our suggestion on how SuperDARN could be used as a potential tool of providing a direct diagnostics on how MHD waves in the solar wind could enter into magnetosphere right at the boundary providing improved understanding of large-scale processes on a time scale of a minute. This potential capability of SuperDARN could enable researchers for the first time to test various theories on how energy is transported into the boundary of the magnetosphere in a global scale view through continuous monitoring of the high latitude ionospheric convection. Results in this study support the hypothesis that the coherent phase on open field lines and the discrete frequency FLR at 0.8-mHz were being driven by an external wave source in the solar wind at the same discrete frequency.

Sakaguchi KaoriNICT Japan