2011 SuperDARN Workshop       

Ionospheric Convection and Field-Aligned Currents During Strong Magnetospheric Driving: A SuperDARN/AMPERE Case Study

L.B.N. Clausen (1), J.B.H. Baker (1), J.M. Ruohoniemi (1), B.J. Anderson (2)
(1) Space@VT, Virginia Tech, Blacksburg, Virginia, USA
(2) Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA

abstract. We present a detailed case study of the dynamic response of ionospheric convection and field-aligned currents (FACs) to abrupt changes in the interplanetary magnetic field (IMF) on December 12th 2010. Between 1900 and 2000 UT the IMF was strongly northward (Bt > 6 nT) and the SuperDARN radars in the northern hemisphere observed characteristic reverse convection cells on the dayside typically associated with high-latitude reconnection. However, the FACs measured by the AMPERE project during this time show no signature of the expected NBZ current system. Around 2000 UT the IMF turned southward (Bt ~ 10 nT) and following this reversal, the ionospheric convection changed into the typical two-cell pattern associated with dayside reconnection. As the IMF continued to stay southward for 2 hours, the increased solar wind-magnetosphere coupling manifested itself as higher convection velocities observed by SuperDARN radars, higher cross polar cap potential, increasing FAC i ntensity and an equatorward motion of the FAC location. We interpret the motion of the FACs as a signature of increasing open magnetic flux within the polar cap consistent with dayside reconnection due to southward IMF. The spatial patterns of DMSP satellite observations of auroral boundaries support this claim. Ionospheric convection and the FAC intensity are found to be in good agreement, specifically we find that intense FACs are co-located with strong velocity shears. The combined AMPERE-SuperDARN dataset allows us to study the response of ionospheric convection and FACs to solar wind driving on an unprecedented time scale of minutes.

Sakaguchi KaoriNICT Japan