Connections between X, EUV/UV and VIS solar activity

Abstract

With varying solar activity, the solar VIS, UV, EUV, and X-ray emissions from the chromosphere, transition region, and corona all change, but these variations are known to be nonlinear. We use analytical models based on first principles to discuss possible reasons for these nonlinearities. Particularly noteworthy are: increasing competition between chromospheric flux tubes with increasing magnetic flux density; increasing transition region pressure; increasing average coronal loop size and specific change of the loop shape; and nonconductive heat addition to the transition region. We also show why simple geometric volume vs. area arguments are insufficient to explain the observations.