COMBINED MEASUREMENTS OF EISCAT AND THE EISCAT MAGNETOMETER CROSS TO STUDY OMEGA BANDS

A combination of incoherent scatter radar data and data from a magneto meter array complement each other in an ideal way. The magnetometer re sults help to distinguish between temporal and spatial fluctuations in the radar data, and the radar results provide a means to separate mag netometer-inferred equivalent currents into their Hall and Pedersen co mponents. The technique is used to study OMEGA bands and leads to a be tter understanding of the ionospheric current structure associated wit h this phenomenon. In extending previous models we propose a pair of c ounterrotating source free ionospheric current vortices driven by fiel d-aligned currents, an upward current centered in the luminous part of the OMEGA band and a downward current in the dark part with its cente r about 400 km west of the upward current.