OBSERVATIONS OF THERMOSPHERIC NEUTRAL WINDS WITHIN THE POLAR CUSP ANDTHE AURORAL OVAL USING A DOPPLER IMAGING-SYSTEM (DIS)

Two Doppler imaging systems (DIS) or wide-field imaging Fabry-Perot in terferometers (FPI), have recently been commissioned, one at the Auror al Station, Adventdalen, Longyearbyen, Svalbard, and the second at the IRF, Kiruna, Sweden. These instruments can provide wide-field (600 800 km) images of neutral wind flows in the upper thermosphere, by mea suring the Doppler shift of the atomic oxygen forbidden near 630 nm, w hich is emitted from an altitude of approximately 240 km. From the ins trument in Svalbard, at mid-winter, it is possible to observe the days ide polar cusp and the polar cap throughout the entire day, whereas fr om Kiruna, the night-time auroral oval is observable during the hours of darkness. Measurements of thermospheric dynamics from the DIS can b e used in conjunction with observations of ionospheric plasma flows an d thermal plasma densities by the EISCAT-Svalbard radar (ESR) and by E ISCAT, along with other complementary observations by co-located instr uments such as the auroral large-scale imaging system (ALIS). Such com bined data sets will allow a wide range of scientific studies to be pe rformed concerning the dynamical response of the thermosphere and iono sphere, and the important energetic and momentum exchange processes re sulting from their complex interactions. These processes are particula rly important in the immediate vicinity of the polar cusp and within t he auroral oval. Early results from Svalbard in late 1995 will be disc ussed. The DIS in Kiruna observed two interesting geomagnetic disturba nces in early 1997, the minor geomagnetic storm of 10, 11 January, and the disturbed period from 7-10 February. During these events, the the rmospheric wind response showed some interesting departures from the a verage behaviour, which we attribute to the result of strong and varia ble Lorenz forcing (ion drag) and Joule and particle heating during th ese geomagnetic disturbances.