Changed Relation Between Radio Flux F10,7 And Some Solar Activity Indices During Cycles 21 - 23

TL;DR

This study investigates the cyclic variations in correlation between radio flux F10,7 and various solar activity indices over solar cycles 21-23, revealing a stable approximately 5.5-year periodicity.

Contribution

It identifies a stable cyclicity in the correlation coefficients between solar activity indices and F10,7, highlighting a previously unreported periodic behavior.

Findings

Correlation coefficients exhibit cyclic variations with a period of about 5.5 years.

Multiple solar activity indices show similar cyclic correlation patterns.

The cyclicity is consistent across solar cycles 21 to 23.

Abstract

A stable cyclicity of correlation coefficients Kcorr for some solar activity indices versus F10,7 was found after monthly averages values analysis. These indices are: Wolf numbers, 10,7 cm radio flux F10,7, 0,1-0,8 nm background, the total solar irradiance, Mg II UV-index (280 nm core to wing ratio) and counts of flares. The correlation coefficients of the linear regression of these solar activity indices versus F10,7 were analyzed for every year in solar cycles 21 - 23. We found out that the values of yearly determined correlation coefficients Kcorr for solar activity indices versus F10,7 show the cyclic variations with stable period closed to half length of 11-year cycle (5,5 years approximately)