Neutral temperature and winds from EISCAT CP-3 observations

Abstract

From EISCAT observations, ion temperature and density and electron temperature distributions versus latitude and time are obtained at 325 km altitude, together with E × B drifts of the ions. Assuming a neutral concentration from a model, one analyses the ion energy equation in order to get information on the neutral temperature and wind distributions. In a first step, one expands the neutral temperature versus latitude and time with analytical polynomials by solving the ion energy equation in which frictional effects are neglected. However, periods of high convection velocities are not taken into account for Tn estimates. One gets, therefore, a neutral temperature model which best fits the data outside the regions and the periods where frictional heating is suspected to be important. In a second step, one can then use this temperature model to solve the ion energy equation during the periods of large frictional heating, getting, therefore, the frictional term. Using the central position of the scan in order to deduce the meridional neutral wind from field-aligned ion velocities, the zonal component of the neutral wind can henceforth be estimated. Examples of such an approach are shown, in particular for the Global Thermospheric Modelling Study period in June 1984.