Detection of Large Scale TIDs associated with the dayside cusp using SuperDARN measurements

Parameter variations for the dayside ionosphere as a result of a Large-Scale Acoustic Gravity Wave were studied for the 17 February 1998 substorm using the SuperDARN radar network measurements. This substorm was characterised by a sharp rise in the AE index with the maximum of ~900 nT. The source of this disturbance was located at the plasma convection throat and in the dayside cusp region. The location of the source was obtained from studies of the number of datasets including high-latitude convection map, data from 4 DMSP satellites and the network of ground based magnetometers. Parameters of the two wave-like disturbances were deduced using measurements from 6 SuperDARN radars, including Goose Bay and Kapuskasing, and the Goose Bay ionospheric station data. These parameters are: the wave periods of 1.5 h and 2 h, the velocity of ~400 m/s for both, and the wavelengths of 2200 km and 2900 km respectively. These disturbances were clearly registered as skip distance variations on Goose Bay and Kapuskasing radars. At the same time, these disturbances would be difficult to deduce from the ground based ionospheric station data alone, because hmF2 variations were 10-40 km only and NmF2 variations were 10-20% only. This method of wave-like ionospheric parameter variation study was verified using simulation with the deduced parameters an input. The results show a good agreement with radar measurements. Thus, it was demonstrated that SuperDARN radar measurements can be very useful for the fine wave-like parameter variation studies in the dayside subauroral ionosphere.