Ionospheric dynamics in the central polar cap

The Eureka polar observatory located near the northern magnetic pole permits a quasi-continuous optical view of the central polar region down to 80° corrected geomagnetic latitude, through the dark winter night from November through February. Two key instruments operating there are an all sky imager (5577 and 6300 Å) and a multichannel photometer which scans the dawn-dusk meridian each 40 s. The photometer has monitored 5577 and 6300 Å polar airglow. These show much dynamical behaviour, in addition to a general decline in intensities from 1991–1992 (from 195 R to 100 R for 558 Å and from 180 R to 60 R for 6300 Å). Polar auroral arcs are seen much of the time when the interplanetary magnetic field B z is positive, but polar extensions of auroral oval phenomena are also seen during major auroral disturbances such as the ones on November 8–9, 1991, November 4, 1993 and February 21, 1994. With thresholds of detectability of about 50 R above airglow levels, drifting F-layer patches are seen much of the time when B z is negative. Their occurrence patterns and response to interplanetary magnetic field changes have been analyzed using data from the past 6 winters. Some of these results are discussed in relation to opportunities for collaborations with new radar facilities in the auroral oval-polar cap interface region.