Drifting F-Layer Patches over the Magnetic Pole.

Establishment of a polar observatory at Eureka, Canada in 1991 has permitted studies of F-layer ionization patches drifting over the north magnetic pole, using a multi-channel photometer and a digital ionosonde. Optical characteristics of two typical patches are shown. A case study of a sequence of several patches observed on February 17, 1993 is reported. Their optical intensities as determined from 630 and 558 nm meridian photometer scans averaged 200 R and 50 R respectively above airglow background. Their drift velocities through zenith, as measured by a digital ionosonde (CADI), averaged about 0.3 km/s while their bulk motion as seen optically was somewhat greater. The first 3 patches of the sequence, from 0945 to 1010 UT, moved generally in an antisunward direction while three immediately following, from 1015 to 1100 UT, had a velocity component in the dawn to dusk direction with a velocity vector rotated a full 90° from the earlier motions.