## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Storm**} & \multicolumn{2}{c}{**Darwin**} & \multicolumn{2}{c}{**Townsville**} & \multicolumn{2}{c}{**Canberra**} \\ \cline{2-7}  & _f_**0F2** & _\(\Delta\)_f_0F2 (\%)** & \(f\)0F2** & _\(\Delta\)_f_0F2 (\%)** & \(f\)0F2** & _\(\Delta\)_f_0F2 (\%)** \\ \hline
8–9 March & Increase & \(+\)42.5 & Increase & \(+\)55.9 & Increase & \(+\)50.0 \\
23–24 April & No change & — & No change & — & No change & — \\
14–15 July & Increase & \(+\)230.8 & Increase & \(+\)62.5 & Decrease & \(-\)48.6 \\
30 September–3 October & Decrease & \(-\)42.6 & Decrease & \(-\)39.2 & Decrease & \(-\)63.5 \\
7–9 October & Decrease & \(-\)61.6 & Decrease & \(-\)65.1 & Decrease & \(-\)59.6 \\
13–14 November & Decrease & \(-\)20.2 & Decrease & \(-\)36.8 & Decrease & \(-\)40.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of the ionospheric response during the recovery phase for six intense geomagnetic storms at Darwin, Townsville, and Canberra stations during 2012. For the detailed variation of \(f\)0F2 at Darwin and Canberra stations during 14–15 July storm, the reader is referred to the paper by [PERSON] and [PERSON] [7]. during dayside (nightside) and produce ionospheric effects during the recovery phase of the storms. During the recovery phase, 8-9 March storm showed positive ionospheric storm at all three stations and interestingly 14-15 July storm showed a positive ionospheric storm at Darwin and Townville stations and delayed negative ionospheric storm at the mid-latitude station, Canberra. [PERSON] and [PERSON] [7] have studied and discussed the effects of 14-15 July ionospheric effects in the southern hemisphere including at the Darwin and Canberra stations. The positive ionospheric storm during the March geomagnetic storm occurred at the local nighttime of the stations when the quiet-time ionospheric electric field is westward and \(\mathbf{E}\times\mathbf{B}\) drifts are downward. The positive ionospheric effect during the March geomagnetic storm accounted for the dominant effect of nighttime DDEFs which would change the normal downward ionospheric drifts or even reverse to the upward direction and hence produce an increase in the electron density or \(f\)0F2 as occurred at Darwin and Townville during their local nighttime. However, in Canberra, the negative ionospheric storm due to July geomagnetic storm occurred during its local daytime (06-20 LT) and accounted for the combined effects of the westwards DDEFs during local daytime which would reduce the normal upward ionospheric drifts and for equatorward storm-time motion of the thermospheric neutral winds with decreased O/N\({}_{2}\) density ratio due to upwelling of gas with reduced O/N\({}_{2}\) ratio at high latitude moving toward the low latitudes. A long duration decrease in \(f\)0F2 was found for geomagnetic storms of 30 September-3 October (Figures 1-3), 7-8 October (Figures 4-6), and 13-14 November storms during their recovery phases. The mid-latitude station (Canberra) for these storms showed the longest duration of negative ionospheric storms and least by the Darwin station (e.g., Figures 1-6). These negative ionospheric storms are accounted for combined effects DDEFs and equatorward storm-time thermospheric neutral winds with decreased O/N\({}_{2}\) density ratio due to upwelling O/N\({}_{2}\) ratio at high latitude moving toward the low latitudes with dominating effect of the latter mechanism. During the recovery phase, the overshielding electric field would also have contributed to the ionospheric effects during these storms by instantly imposing additional ionospheric zonal electric fields in the opposite directions in dayside and nightside, respectively [12].