2011 SuperDARN Workshop       

Dynamic sub-auroral ionospheric electric fields observed by the Falkland Islands radar during the course of a geomagnetic storm

A. Grocott (1), S.E. Milan (1), J.B.H. Baker (2), M.P. Freeman (3), M. Lester (1), and T.K. Yeoman (1)
(1) Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, U.K.
(2) Bradley Department of Electrical and Computer Engineering, Virginia tech., Blacksburg, VA 24061, U.S.
(3) British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge, CB3 0ET, U.K.

abstract. We present an analysis of ionospheric electric field data observed during a geomagnetic storm by the recently deployed Falkland Islands SuperDARN radar. On 3 August 2010 at ~1800 UT evidence of the onset of a geomagnetic storm was observed in ground magnetometer data in the form of a decrease in the Sym-H index of ~100 nT, indicative of an enhancement in the strength of the ring current. The main phase of the storm was observed to last ~24 hours before a gradual recovery lasting ~3 days. On 4 August, during the peak magnetic disturbance of the storm, a high velocity (>1000 m/s) channel of ionospheric plasma flow, which we interpret as a sub-auroral ion drift (SAID), located between 53 and 58 degrees south and lasting ~6.5 hours, was observed by the Falkland Islands radar in the pre-midnight sector. Coincident data from the magnetically near-conjugate northern hemisphere Blackstone HF radar confirm the existence of a similar feature located at the equivalent nor thern latitude. In this paper we discuss the influence of the storm on the ionospheric conditions and describe a detailed investigation of the high velocity flow channel. We find that variations in latitude and magnitude of the flows in the channel are related to both the ring current dynamics and variations in the inferred size of the polar cap, suggesting that the electrodynamics of the nightside sub-auroral region are driven by a combination of solar wind driving and processes occurring in the inner magnetosphere.

Sakaguchi KaoriNICT Japan