Frequency of Solar Spotless Days and Flare Index as Indices of Solar Cycle Activity

다국어 초록 (Multilingual Abstract)

There was a research on the prolongation of solar cycle 23 by the solar cyclic variation of solar, interplanetary geomagneticparameters by Oh & Kim (2013). They also suggested that the sunspot number cannot typically explain the variation of totalsolar irradiance any more. Instead of the sunspot number, a new index is introduced to explain the degree of solar activity.
We have analyzed the frequency of sunspot appearance, the length of solar cycle, and the rise time to a solar maximumas the characteristics of solar cycle. Then, we have examined the predictability of solar activity by the characteristics ofpreceding solar cycle. We have also investigated the hemispheric variation of flare index for the periods that the leadingsunspot has the same magnetic polarity. As a result, it was found that there was a good correlation between the length ofpreceding solar cycle and spotless days. When the length of preceding solar cycle gets longer, the spotless days increase.
It is also shown that the shorter rise time to a solar maximum is highly correlated with the increase of sunspots at a solarmaximum. Therefore, the appearance frequency of spotless days and the length of solar cycle are more significant thanthe general sunspot number as an index of declining solar activity. Additionally, the activity of flares leads in the northernhemisphere and is stronger in the hemisphere with leading sunspots in positive polarity than in the hemisphere withleading sunspots in negative polarity. This result suggests that it is necessary to analyze the magnetic polarity’s effect on theflares and to interpret the period from the solar maximum to solar maximum as the definition of solar cycle.

참고문헌 (Reference)

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