Large Scale Traveling Ionospheric Disturbances during geomagnetic storms in the Australian region

Large-scale travelling ionospheric disturbances (LSTIDs) are detected using the critical frequency of the $F_{2}$ layer $( f_{o}F_{2})$ of the ionosphere. The HF interferometry (HF-Int) technique is applied to the network of ionosondes in the Australian region to detect and estimate propagation parameters. Here we present traveling ionospheric disturbances (TIDs) characteristics (period, velocity, and intensity) associated with selected geomagnetic storms. The TID response during geomagnetic storms varies significantly owing to the differing storm evolution patterns. Results show the morphology of parameters detected continually changes with time corresponding to highly dynamic response effects on the ionosphere. TIDs detected had a wide range of velocity magnitudes (mean ± standard deviation) such as $687 \pm 16\mathrm{m} /\mathrm{s}$ during onset phase, $516 \pm 125\mathrm{m} /\mathrm{s}$ during main phase and $569 \pm 91\mathrm{m} /\mathrm{s}$ during the recovery phase of the storm presented here. Propagation directions are predominantly equatorward with east and west deviations owing to higher latitude source generations associated with storm induced intensifications. The HF-Int system uses spectral techniques to estimate the dominant period and outputs the spectral energy contribution (SEC) which is a measure of the contribution of the TID to the total variability of the time series. TID activity levels are based on SEC criteria mostly indicated moderate and weak events with a range of periods 60-140 min.