The radar PMSE overshoot effect as a diagnostic method

The radar phenomenon PMSE (Polar Mesospheric Summer Echoes) which is associated with charged dust particles, can be affected by artificial electron heating. If the heater is run in a cycle with equal, and comparatively short (10-20 sec) off and on periods, the PMSE strength is observed to weaken when the heater is on, and recover to approximately the same strength when the heater is switched off (Chilson et.al 2000). With a new heater cycling, where the heater is on for a short time and then off for a long enough time for the dusty plasma conditions to return to its undisturbed conditions, a PMSE ``Overshoot'' effect is produced (Havnes et.al 2003). In the overshoot the PMSE strength, when the heater is switched off, can increase by a factor of several compared to what it was directly before the heater was switched on. By analysing the shape of the overshoot characteristic curve as the PMSE varies through a weakening as the heater is switched on, an overshoot as it is switched off and a subsequent relaxation back to an unaffected strength, we can obtain a considerable amount of information on the state of the PMSE dusty plasma. In the present paper we will show results from the first Eiscat overshoot campaign in 2003, and preliminary results from a planned Eiscat overshoot campaign in July 2004. In the new campaign we will observe with a higher time-resolution, compared to in 2003, to obtain a more accurate overshoot intensity curve as function of time. We will also investigate the effects of different heater cycling. Chilson, P.B., E. Belova, M.T. Rietveld, S. Kirkwood, and U.-P. Hoppe, J. Geophys. Res.Lett., 27 , 3801, 2000. Havnes, O., C. La Hoz, L.I. Næsheim, and M.T. Rietveld, Geophys. Res. Lett, 30, 2229, 2003.