Optical airglow patches in relation to EISCAT Svalbard Radar electron density measurements

Abstract : Drifting polar cap patches are localized regions of enhanced F-region plasma densities with scale sizes of several hundreds of kilometre. The patches are seen to drift antisunward with velocities of several hundreds meters per second, and can have densities up to 10 times the ambient background. We present simultaneous ground based optical and radar data of nightside polar cap patches. Using meridian scanning photometer data, the optical airglow signature of patches are seen to drift into the auroral oval. The field aligned radar shows high electron density, with low electron temperature during the period of interest. This indicates that there is no electron precipitation in the radar field of view, and that the radar electron density signal stems from the drifting polar cap patches. It is seen that there is a very good match between enhancements in the 6300 Å airglow signature and enhancements in the radar electron density measurements.