TY - JOUR
T1 - Spatial distribution of average vorticity in the high-latitude ionosphere and its variation with interplanetary magnetic field direction and season
AU - Chisham, G.
AU - Freeman, M. P.
AU - Abel, G. A.
AU - Bristow, W. A.
AU - Marchaudon, A.
AU - Ruohoniemi, J. M.
AU - Sofko, G. J.
PY - 2009
Y1 - 2009
N2 - We present a technique to measure the magnetic field-aligned vorticity of mesoscale plasma flows in the F region ionosphere using line-of-sight velocity measurements made by the Super Dual Auroral Radar Network (SuperDARN). Vorticity is often used as a proxy for magnetic field-aligned current (FAC) intensity in the ionosphere but also provides information about turbulent processes in the ionosphere and magnetosphere. Using 6 years (2000-2005 inclusive) of vorticity measurements made by six SuperDARN radars in the Northern Hemisphere, we have compiled, for the first time, maps of average vorticity across the northern polar ionosphere. These maps have been subdivided according to different seasonal and interplanetary magnetic field (IMF) conditions. The variations in the morphology of the vorticity maps with IMF direction match very closely those seen in maps of average FAC intensity (determined using different methods and instrumentation), suggesting that vorticity is a good proxy for FAC in an averaged sense. The variations in the morphology of the vorticity maps with season show differences from those seen in the FAC maps, illustrating that ionospheric conductance plays a major role in determining the differences between measurements of vorticity and FAC.
AB - We present a technique to measure the magnetic field-aligned vorticity of mesoscale plasma flows in the F region ionosphere using line-of-sight velocity measurements made by the Super Dual Auroral Radar Network (SuperDARN). Vorticity is often used as a proxy for magnetic field-aligned current (FAC) intensity in the ionosphere but also provides information about turbulent processes in the ionosphere and magnetosphere. Using 6 years (2000-2005 inclusive) of vorticity measurements made by six SuperDARN radars in the Northern Hemisphere, we have compiled, for the first time, maps of average vorticity across the northern polar ionosphere. These maps have been subdivided according to different seasonal and interplanetary magnetic field (IMF) conditions. The variations in the morphology of the vorticity maps with IMF direction match very closely those seen in maps of average FAC intensity (determined using different methods and instrumentation), suggesting that vorticity is a good proxy for FAC in an averaged sense. The variations in the morphology of the vorticity maps with season show differences from those seen in the FAC maps, illustrating that ionospheric conductance plays a major role in determining the differences between measurements of vorticity and FAC.
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U2 - 10.1029/2009JA014263
DO - 10.1029/2009JA014263
M3 - Article
AN - SCOPUS:72049100769
VL - 114
JO - Journal of Geophysical Research: Space Physics
JF - Journal of Geophysical Research: Space Physics
SN - 2169-9380
IS - 9
M1 - A09301
ER -