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 17 such storms occurred during Solar Cycles 23 and 24. 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 = 0.73), \(I(E_{y})\) (CC = 0.86), and \(I(Q)\) (CC = 0.94) suggests 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. The results also suggest that the impact of \(B_{s}\) on the great geomagnetic storm intensity is much more significant than that of the solar wind speed and the dynamic pressure during the main phase of an associated great geomagnetic storm. The better estimation of the intensity of an extreme geomagnetic storm intensity based on solar wind parameters is also discussed.

我们使用\（\ Delta \） SYM-H捕获在地磁风暴的主要阶段中SYM-H指数的变化。我们将大地磁暴定义为\（\ Delta \） SYM-H \（\ le -200 \）  nT。分析未由太阳风遮蔽数据之后，我们确定在太阳周期23和24，我们为向南星际磁场分量来计算时间积分发生17级这样的风暴\（I（B_ {S}）\） ，所述太阳风电场\（I（E_ {y}）\）以及\（E_ {y} \）和大地磁主相期间太阳风动压\（I（Q）\）的组合风暴。强度之间的相关系数（CC）\（\ Delta \） SYM-H和三个积分\（I（B_ {s}）\）（CC = 0.73），\（I（E_ {y}）\）（CC = 0.86）和\（I（Q）\）（CC = 0.94）表明，涵盖太阳风电场和太阳风动压的\（Q \）是决定大地磁风暴强度的主要驱动因素。结果还表明，\（B_ {s} \）对大地磁风暴强度的影响比相关的大地磁风暴主阶段太阳风速和动压的影响要大得多。还讨论了基于太阳风参数对极端地磁风暴强度的更好估计。