[pibach]

Siehe auch https://en.wikipedia.org/wiki/Modern_Maximum

Dazu aus A history of solar activity over millennia":



Grand maxima of solar activity
4.3.1 The modern episode of active sun
In the last decades we were living in a period of a very active sun with a level of activity that is very high for the last few centuries covered by direct solar observation. The sunspot number was growing rapidly between 1900 and 1940, with more than a doubling average group sunspot number, and has remained at that high level until recently (see Fig. 1). Note that growth comes mostly from raising the cycle maximum amplitude, while sunspot activity always returns to a very low level around solar cycle minima. While the average group sunspot number (using GSN) for the period 1750–1900 was 35±935±9 ( 39±639±6 , if the Dalton minimum in 1797–1828 is not counted), it stands high at the level of 75±375±3 for 1950–2000. Therefore, the modern active sun episode, which started in the 1940s, can be regarded as the modern grand maximum of solar activity, as opposed to a grand minimum (Wilson 1988b). As discussed by Clette et al. (2014, see their Figure 65), the number of spotless days during cycles 12–22 was half of that for another relatively high activity period ca. 1850. This again suggests the uniqueness of the modern grand maximum on the centennial time scale. The reality of the Modern grand maximum was independently confirmed by Ziȩba and Nieckarz (2014) who have shown, by studying active versus passive (spotless) days that cycles 17–23 were more active, compared to cycles 8–15.

Although uncertainties in sunspot numbers during the 18th and 19th centuries (see discussion in Sect. 2.2.1) make it a bit unclear on the centennial time scale, data on cosmogenic isotopes (Usoskin et al. 2003c; Solanki et al. 2004; Inceoglu et al. 2015) imply that such high activity episodes occur quite seldom.

However, as we can securely say now, after the very weak solar minimum in 2008–2009 (e.g., Gibson et al. 2011), solar activity returns to its normal moderate level in cycle # 24. Thus, the high activity episode known as the Modern grand maximum is over.

Is such high solar activity typical or is it something extraordinary? While it is broadly agreed that the modern active sun episode is a special phenomenon, the question of how (a)typical such upward bumps are from “normal” activity is a topic of hot debate.