The present investigation attempts to quantify the temporal variation of Solar Flare Index (SFI) with other activity indices during solar cycles 21 – 24 by using different techniques such as linear regression, correlation, cross-correlation with phase lag-lead, etc. Different Solar Activity Indices (SAI) considered in this present study are Sunspot Number (SSN), 10.7 cm Solar Radio Flux (F10.7), Coronal Index (CI) and MgII Core-to-Wing Ratio (MgII). The maximum cycle amplitude of SFI and considered SAI has a decreasing trend from solar cycle 22, and cycle 24 is the weakest solar cycle among all other cycles. The SFI with SSN, F10.7, CI and MgII shows hysteresis during all cycles except for solar cycle 22 where both paths for ascending and descending phases are intercepting each other, thereby representing a phase reversal. A positive hysteresis circulation exists between SFI and considered SAI during solar cycles 22 and 23, whereas a negative circulation exists in cycles 21 and 24. SFI has a high positive correlation with coefficient values of 0.92, 0.94, 0.84 and 0.81 for SSN, F10.7, CI and MgII respectively. According to cross-correlation analysis, SFI has a phase lag with considered SAI during an odd-number solar cycle (solar cycles 21 and 23) but no phase lag/lead during an even-numbered solar cycle (solar cycles 22 and 24). However, the entire smoothed monthly average SFI data indicate an in-phase relationship with SSN, F10.7 and MgII, and a one-month phase lag with CI. The presence of those above characteristics strongly confirms the outcomes of different research work with various solar indices and the highest correlation exists between SFI and SSN as well as F10.7 which establishes that SFI may be considered as one of the prime activity indices to interpret the characteristics of the Sun’s active region as well as for more accurate short-range or long-range forecasting of solar events.

本研究试图通过使用不同的技术，如线性回归、相关、与相位滞后超前的互相关等，量化太阳耀斑指数 (SFI) 与其他活动指数在太阳周期 21-24 期间的时间变化。本研究中考虑的活动指数 (SAI) 是太阳黑子数 (SSN)、10.7 厘米太阳射电通量 (F10.7)、日冕指数 (CI) 和 MgII 核翼比 (MgII)。SFI 和考虑的 SAI 的最大周期幅度从太阳周期 22 开始呈下降趋势，周期 24 是所有其他周期中最弱的太阳周期。具有 SSN、F10.7、CI 和 MgII 的 SFI 在所有周期中都显示出滞后现象，除了太阳周期 22，其中上升和下降阶段的两条路径相互交叉，从而代表相位反转。在太阳周期 22 和 23 期间，SFI 和考虑的 SAI 之间存在正滞后环流，而在太阳周期 21 和 24 中存在负环流。SFI 与 SSN、F10 的系数值为 0.92、0.94、0.84 和 0.81 具有高度正相关。 7，CI和MgII分别。根据互相关分析，在奇数太阳周期（太阳周期 21 和 23）期间，SFI 与考虑的 SAI 有相位滞后，但在偶数太阳周期（太阳周期 22 和 24）期间没有相位滞后/超前。然而，整个平滑的月平均 SFI 数据表明与 SSN、F10.7 和 MgII 存在同相关系，与 CI 存在 1 个月的相位滞后。