Sunspot Magnetic Field Measurements at MWO and CrAO: Radio Emission F10.7 during the Declining and Minimum Phase of Solar Cycle 24

Abstract

A comparative analysis of the evolution of the maximum magnetic field of sunspots, obtained at Mount Wilson Observatory (9033 measurements) and the spectral flux of radio emission at a frequency of 2.8 GHz (F_10.7) during the declining and minimum phase of solar cycle 24 (2014–2019), is carried out. An anomalous behavior of the magnetic field of sunspots with a strength of 1500 G or higher has been detected, which is characterized by even a slight increase in the sunspot magnetic field during the declining phase of the cycle, which is in a good agreement with the results of observations by the BST-2 telescope of the Crimean Astrophysical Observatory and with measurements of the areas of the biggest spot in a group according to the data of the Kislovodsk Mountain Astronomical Station. Despite a noticeable increase in the average values of the magnetic field from 2015 to 2017, no significant changes were found in the scatter diagram of the F_10.7 solar activity index and Wolf numbers. This indicates the decisive contribution to the index F_10.7 of the thermal bremsstrahlung mechanism of radio emission.