On red shifs in the transition region and corona

TL;DR

This paper demonstrates that episodic heating models with specific scale heights naturally produce red-shifts in the solar transition region, supported by 3D MHD simulations of the upper solar atmosphere.

Contribution

It introduces 3D MHD models that replicate transition region red-shifts by incorporating episodic heating and magnetic flux emergence.

Findings

Red-shifts are produced in models with heating scale heights between 200 km and 50 Mm.

3D MHD simulations include upper convection zone to corona, up to 15 Mm above photosphere.

Magnetic field stressing and flux emergence contribute to heating in the models.

Abstract

We present evidence that transition region red-shifts are naturally produced in episodically heated models where the average volumetric heating scale height lies between that of the chromospheric pressure scale height of 200 km and the coronal scale height of 50 Mm. In order to do so we present results from 3d MHD models spanning the upper convection zone up to the corona, 15 Mm above the photosphere. Transition region and coronal heating in these models is due both the stressing of the magnetic field by photospheric and convection `zone dynamics, but also in some models by the injection of emerging magnetic flux.