Ground‐based observations of ion/neutral coupling at Thule and Qânâq, Greenland

Abstract

During December 1988, 24 hours of darkness and clear sky conditions permitted continuous observations of the O I (6300 Å) airglow by a Fabry‐Perot interferometer located at Thule Air Base, Greenland. Thus a continuous record of the F region neutral winds was obtained for that month. During this same time period, a digital ionosonde located at Qânâq, Greenland (110 km north of Thule Air Base), was in operation measuring electron density profiles and F region ion drifts. This combination of ground‐based observations allowed the investigation of ion/neutral coupling at a temporal resolution of about 15 min. Interplanetary magnetic field (IMF) data from the IMP 8 satellite were also available from December 16 to 24 and indicated intervals of Bz northward IMF conditions during this period. Here we investigate the observed response of the neutral wind to convection changes in the ion drift inside the polar cap for southward and northward IMF Bz conditions. In particular, we establish a control day illustrating the typical antisunward neutral wind and ion drift patterns observed for southward Bz over Thule and Qânâq, and we compare it with observations made when the IMF Bz is directed northward. The observations during periods of northward Bz display sunward directed ion drifts over the polar cap accompanied by decreasing antisunward directed neutral winds. We investigate these times of northward Bz further and demonstrate that the ion drag term alone cannot describe the observed response in the neutral wind during northward IMF.