Coupling Photosphere and Corona: Linear and Turbulent Regimes

TL;DR

This paper investigates how high-frequency and turbulent effects influence the coupling between the photosphere and corona in magnetic loops, showing that coupling persists under most turbulent damping conditions and the coronal field saturates.

Contribution

It introduces an analytical model to study the impact of turbulence and high-frequency effects on photosphere-corona coupling in magnetic loops.

Findings

Coupling persists unless turbulence is fully damped during loop traversal.

Coronal magnetic field saturates at finite values due to photospheric motions.

High-frequency effects and turbulence influence the transmission of movements along magnetic loops.

Abstract

In a recent work Grappin et al. [1] have shown that low- frequency movements can be transmitted from one footpoint to the other along a magnetic loop, thus mimicking a friction effect of the corona on the photosphere, and invalidating the line-tying approximation. We consider here successively the effect of high frequencies and turbulent damping on the process. We use a very simple atmospheric model which allows to study analytically the laminar case, and to study the turbulent case both using simple phenomenological arguments and a more sophisticated turbulence model [2]. We find that, except when turbulent damping is such that all turbulence is damped during loop traversal, coupling still occurs between distant footpoints, and moreover the coronal field induced by photospheric movements saturates at finite values.