Dependence of great geomagnetic storm intensity ($\Delta$SYM-H$\le$-200 nT) on associated solar wind parameters

We use $\Delta$SYM-H to capture the variation in the SYM-H index during the main phase of a geomagnetic storm. We define great geomagnetic storms as those with $\Delta$SYM-H $\le$ -200 nT. After analyzing the data that were not obscured by solar winds, we determined that 11 such storms occurred during solar cycle 23. We calculated time integrals for the southward interplanetary magnetic field component (I(B$_s$)), the solar wind electric field (I(E$_y$)), and a combination of E$_y$ and the solar wind dynamic pressure (I(Q)) during the main phase of a great geomagnetic storm. The strength of the correlation coefficient (CC) between $\Delta$SYM-H and each of the three integrals I(B$_s$) (CC = 0.74), I(E$_y$) (CC = 0.85), and I(Q) (CC = 0.94) suggests that the impact of B$_s$ on the great geomagnetic storm intensity is more significant than that of the solar wind speed and the dynamic pressure during the main phase of associated great geomagnetic storm. Because I(Q) has the highest correlation coefficient, we infer that Q, which encompasses both the solar wind electric field and the solar wind dynamic pressure, is the main driving factor that determines the intensity of a great geomagnetic storm. However, the extreme geomagnetic storm intensity can be estimated by solar wind electric field because the contribution made by solar wind electric field is almost equal to that made by Q for extreme geomagnetic storm.