Abstract
At auroral latitudes the electron heat flow resulting from solar EUV heating, as well as magnetospheric energy input, are important parameters which drive the thermal electron structure of the upper ionosphere. A method is presented which allows a determination from EISCAT‐VHF observations of the heat flow at two altitudes, typical of the collision‐dominated F2 region and of the topside ionosphere. EISCAT midwinter and near‐summer observations are used to illustrate the method: diurnal and seasonal variations of solar origin are evidenced, with peculiar enhancements at sunrise and sunset that are interpreted as a delay between the F2 level and topside terminator passage. Perturbations of magnetospheric origin are then discussed. One of them is characteristic of low‐altitude energy inputs. Others correspond to high‐altitude energy inputs through heat flow variations and are interpreted as upward currents of the order of 14 µA m−2.
Published Version
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