Speaker
Description
Long-term reconstructions of sunspot number (SSN) and group sunspot number (GSN) often tacitly assume that the basic characteristics of solar activity remain unchanged even over long times, e.g., that the sunspots and sunspot groups now and, say, 100 or 500 years ago have the same relations and characteristics. However, this assumption needs examination, especially as the long-term homogeneity between sunspots and several other solar activity parameters has recently been challenged (Mursula et al., 2024).
Here we use long series of sunspot observations to study if and how the number of sunspots per group varies at different time scales. We find that the yearly mean number of sunspots per group varies closely in phase with the solar cycle over the whole 270-year time interval. The yearly sunspot/group ratios vary between about 3 and 10. Moreover, we find that number of sunspots per group depicts a very similar secular (Gleissberg) cyclicity as sunspots.
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