Solar Activity in the Past: From Different Proxies to Combined Reconstruction

Abstract

Using proxy series that includes ancient observations of sunspots and auroras, concentrations of cosmogenic isotopes 14 C and 10 Be, we reconstruct sunspot activity level since 850 AD to the present. As a main reference index of solar activity we use the Wolf sunspot numbers, which, as we demonstrate, reflect true levels of the activity in the 18th and 19th centuries better than the Group sunspot numbers. We construct a set of linear and nonlinear inductive models, which are in a good agreement with each other and reproduce the known global solar activity extrema. According to our results, amplitudes of the global maxima are in intermediate positions in respect to estimations of other authors. It follows from our reconstructions that the global maximum of the 20th century is not much higher, if at all, than others.

What characterizes planetary space weather?

“…On some occasions, the velocity increases while the density decreases. However, this is not a general feature since both can increase at the same time, especially during a long series of solar events (Miletsky et al 2004;Richardson and Cane 2012a, b).…”

“…During active events, it may reach values larger than 50 nT (Miletsky et al 2004). The direction of the magnetic field is usually in the well-established "Parker Spiral" (Parker 1958) orientation, determined by the solar rotation rate of the highly conducting, frozen-in solar wind plasma (about 27 days on average).…”

Astrophysics in 2005

“…Long-term solar activity reconstruction on centennial to multi-millennia timescales is accomplished by cosmogenic isotope records, such as 10 Be and 14 C (Miletsky et al 2004;Mordvinov et al 2004;Lee et al 2004;Volobuev 2004), which are produced mostly in the upper atmosphere, and thus are anticorrelated with the sunspot number (Scherer et al 2004), but this archeo-magnetic reconstruction method is not really a measurement but rather a "postdiction," and thus is not considered reliable for future predictions (Usoskin & Kovaltsov 2004). Some authors defined a new parameter to characterize the longterm solar cycle variability, the sunspot unit area, which is the size of a sunspot averaged over a cycle, but then lost the Waldmeier effect and the Gnevyshew-Ohl rule (Li et al 2005d).…”