Observations of omega bands using an imaging riometer

Abstract. We present a case study of an omega band current system from 11 May 1998 using data from the Imaging Riometer for Ionospheric Studies (IRIS) in Finland. For the first time, images of a substorm-related omega band in cosmic noise absorption are shown. The substorm in question was one of a string that occurred on that day; inspection of geostationary satellite data indicates that this was a sawtooth event. Using a previously established statistical relationship, the IRIS data is used to provide maps of Hall conductance and compared with previous estimates utilising both HF and VHF coherent-scatter radars. Discrepancies are discussed with reference to precipitation spectrum and the geometry of the experimental set-up. The imaging riometer data provides a higher spatial resolution than the combined magnetometer-radar pairing for determining the Hall conductance and can also be used to identify the extent of the precipitation in the absence of optical data.