Measurements of Photospheric and Chromospheric Magnetic Field Structures Associated with Chromospheric Heating over a Solar Plage Region

Tetsu Anan,Carlos Dominguez-Tagle,Manuel Collados,Lucia Kleint,Lucas A Tarr,Gabriel I Dima,Sarah A Jaeggli,Thomas A Schad,Reizaburo Kitai

doi:10.3847/1538-4357/ac1b9c

Abstract

Abstract In order to investigate the relation between magnetic structures and the signatures of heating in plage regions, we observed a plage region with the He i 1083.0 nm and Si i 1082.7 nm lines on 2018 October 3 using the integral field unit mode of the GREGOR Infrared Spectrograph (GRIS) installed at the GREGOR telescope. During the GRIS observation, the Interface Region Imaging Spectrograph obtained spectra of the ultraviolet Mg ii doublet emitted from the same region. In the periphery of the plage region, within the limited field of view seen by GRIS, we find that the Mg ii radiative flux increases with the magnetic field in the chromosphere with a factor of proportionality of 2.38 × 104 erg cm−2 s−1 G−1. The positive correlation implies that magnetic flux tubes can be heated by Alfvén wave turbulence or by collisions between ions and neutral atoms relating to Alfvén waves. Within the plage region itself, the radiative flux was large between patches of strong magnetic field strength in the photosphere or at the edges of magnetic patches. On the other hand, we do not find any significant spatial correlation between the enhanced radiative flux and the chromospheric magnetic field strength or the electric current. In addition to the Alfvén wave turbulence or collisions between ions and neutral atoms relating to Alfvén waves, other heating mechanisms related to magnetic field perturbations produced by interactions of magnetic flux tubes could be at work in the plage chromosphere.

Highlights

Since the temperature in the solar chromosphere and corona is higher than that expected for a state of radiative equilibrium, some mechanical heating is required to maintain the atmospheric temperature (Athay 1966; Withbroe & Noyes 1977; Vernazza et al 1981; Anderson 1989)
In order to distinguish the heating mechanisms operating in the chromosphere over plage regions, we investigate relations between the heating energy flux and the magnetic field in the photosphere and the chromosphere
The Mg II h & k radiative cooling energy flux maps display where chromospheric heating occurs because about 15% of the radiative energy is released as emissions of the Mg II lines (Avrett 1981; Vernazza et al 1981)

Summary

Introduction

Since the temperature in the solar chromosphere and corona is higher than that expected for a state of radiative equilibrium, some mechanical heating is required to maintain the atmospheric temperature (Athay 1966; Withbroe & Noyes 1977; Vernazza et al 1981; Anderson 1989). High-resolution Interface Region Imaging Spectrograph (IRIS, De Pontieu et al 2014) observations of the Mg II h & k spectral profiles within plage are only currently reproduced using models with high micro-turbulence (Carlsson et al 2015; De Pontieu et al 2015; de la Cruz Rodrıguez et al 2016; da Silva Santos et al 2020). This implies that shocks, torsional motions, or Alfven

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