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Statistical properties of Joule heating rate, electric field and conductancesin the high latitude ionosphere are studied by a unique one-month measurementmade by the EISCAT incoherent scatter radar in Tromsø (66.6 cgmlat) from 6March to 6 April 2006. The data are from the same season (close to vernalequinox) and from similar sunspot conditions (about 1.5 years before thesunspot minimum) providing an excellent set of data to study the MLT andKp dependence of parameters with high temporal and spatial resolution. All the parameters show a clear MLT variation, which is different for low andhigh Kp conditions. Our results indicate that the response of morningsector conductances and conductance ratios to increased magnetic activity isstronger than that of the evening sector. The co-location of Pedersenconductance maximum and electric field maximum in the morning sector producesthe largest Joule heating rates 03–05 MLT for Kp≥3. In the eveningsector, a smaller maximum occurs at 18 MLT. Minimum Joule heating rates inthe nightside are statistically observed at 23 MLT, which is the location ofthe electric Harang discontinuity. An important outcome of the paper are the fitted functions for the Jouleheating rate as a function of electric field magnitude, separately for fourMLT sectors and two activity levels (Kp<3 and Kp≥3). In addition tothe squared electric field, the fit includes a linear term to study thepossible anticorrelation or correlation between electric field andconductance. In the midday sector, positive correlation is found as well asin the morning sector for the high activity case. In the midnight and eveningsectors, anticorrelation between electric field and conductance is obtained,i.e. high electric fields are associated with low conductances. This isexpected to occur in the return current regions adjacent to auroral arcs as aresult of ionosphere-magnetosphere coupling, as discussed by Aikio et al. (2004)In addition, a part of the anticorrelation may come from polarization effectsinside high-conductance regions, e.g. auroral arcs. These observationsconfirm the speculated effect of small scale electrodynamics, which is notincluded in most of the global modeling efforts of Joule heating rate

Statistical properties of Joule heating rate, electric field and conductances at high latitudes