OBSERVATIONS OF NEUTRAL WINDS IN THE POLAR-CAP DURING NORTHWARD IMF

Long term remote observations of neutral winds at F-region altitudes h ave been performed at Thule Air Base (lat. 76.5-degrees-N, long. 69.0- degrees-W), Greenland, and Sondre Stromfjord (lat. 67.0-degrees-N, lon g. 50.9-degrees-W), Greenland. The former site is very close to the ge omagnetic pole, while the latter site is within the polar cap for seve ral hours each night on either side of geomagnetic midnight. Wind data corresponding to clear sky conditions and Kp less-than-or-equal-to 4 were sorted according to the sign of the IMF B(z) component. The avera ged maximum poleward flow near midnight LST was reduced by approximate ly one third during B(z) northward conditions. If the magnitude of B(y ) was less than the magnitude of the northward B(z) component, then th e averaged poleward flow was further reduced by one half. In addition, if B(z) > 5 nT, then sunward directed horizontal neutral winds were o bserved at the very highest latitudes near noon LST.