Radiocarbon version of 11-year variations in the interplanetary magnetic field since 1250

It is known that the interplanetary magnetic field (IMF), which is controlled by solar activity, modulates the flux of galactic cosmic rays (GCRs). Because GCRs are the only source of the C-14 isotope in the atmosphere before the era of atmospheric nuclear tests, the formation rate of this isotope in the atmosphere is one of the few reliable sources of information on solar activity before the initiation of regular telescopic observations. In this study, we solve the inverse problem for the equation of radiocarbon diffusion from the atmosphere into the ocean by calibrating the radiocarbon content in tree rings from 1510 to 1950. We obtain an approximation of 11-year IMF cycles represented by the IDV index from 1872 to 1950. The model extrapolation to the calibration curve for the Korean Peninsula over the time period from 1250 to 1650 makes it possible to calculate the sequence of minima of quasi-11-year cycles since 1250.