Properties of Solar, Interplanetary, and Geomagnetic Index in Active Days

초록

In this study, we have studied properties of solar, interplanetary, and geomagnetic indices for the period from 1976 to 2024 in view of active days and spotless days. Specifically, we have compared the characteristics of monthly spotless days in percent around a solar minimum period for each solar cycle. In addition, we have revisited the slope of the linear relationship between monthly mean sunspot numbers and monthly number of active days and further explored similar relationship with the F10.7 index, solar flare index, mean magnetic field of the Sun, Kp, Ap, Dst, AE indices, as well as the magnitude of interplanetary magnetic field with components of the interplanetary magnetic field. As a result, we have found that the distribution of monthly number of spotless days has a skewed shape in common, yet varies from one solar cycle to another implying that the number of spotless days around the solar minimum can be used as a predictor of the maximum level of solar activity. It is also found that the slope of the linear relationship in solar parameters tends to become steeper as the maximum sunspot number is large. Unlike solar parameters, results from interplanetary and geomagnetic indices reveal a quite dissimilar behavior. We conclude that the study in terms of active (spotless) days assures combination of various solar and interplanetary indices is required to find a more geoeffective parameter.

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