High-latitude plasma convection from Cluster EDI measurements: method and IMF-dependence

摘要: Abstract. We have used vector measurements of the electron drift velocity made by Electron Drift Instrument (EDI) on Cluster between February 2001 and March 2006 to derive statistical maps high-latitude plasma convection. The EDI measurements, obtained at geocentric distances ~4 ~20 RE over both hemispheres, are mapped into polar ionosphere, sorted according clock-angle interplanetary magnetic field (IMF), measured ACE propagated Earth, using best estimates orientation IMF variations. Only intervals stable used, based magnitude a "bias-vector" constructed from 30-min averages. resulting data set consists total 5862 h data. Contour electric potential in ionosphere subsequently derived averaged ionospheric vectors. Comparison with published results Super Dual Auroral Radar Network (SuperDARN) radar low-altitude satellite shows excellent agreement average convection patterns, particular lack mirror-symmetry effects positive negative By, appearance duskward flow component for strongly southward IMF, general weakening flows potentials northerly directions. This lends credence validity assumption underlying mapping data, namely that lines equipotentials. For northward show clear emergence two counter-rotating lobe cells channel sunward them. drops across caps intermediate results.