Intermediate‐term variations of chromospheric and coronal solar flux during high solar cycle 21 activity

Abstract

The solar Lyman‐α emission, the MgII core‐to‐wing ratio, R (MgII c/w ), the 10.7‐cm radio flux, F 10.7 , and the 1–8 Å X rays are compared during high solar cycle 21 activity from 1981–83. Daily variations of the Mg II and Lyman‐α ultraviolet (UV) lines are highly correlated. There is moderate linear correlation between these lines and F 10.7 and poor linear correlation with 1–8 Å X rays. Power spectral analysis indicates that all four fluxes have 27‐day periodicities due to solar rotation while the R (MgII c/w ) and Lyman‐α have noticeable 13‐day periods in the datasets. F 10.7 moderately represents the 27‐day solar UV variations and represents to a lesser degree variations shorter than or longer than rotation variations. X rays are not represented by F 10.7 on intermediate‐term or shorter timescales.