The Plasma $\beta$ in quiet Sun Regions: Multi-Instrument View

Abstract

A joint campaign of several space-borne and ground-based observatories, such as the GREGOR solar telescope, the Extreme-ultraviolet Imaging Spectrometer (EIS), and the Interface Region Imaging Spectrograph (Hinode Observing Plan 381, 11-22 October 2019) was conducted to investigate the plasma $\beta$ in quiet sun regions. In this work, we focus on October 13, 17, and 19, 2019, to obtain the plasma $\beta$ at different heights through the solar atmosphere based on multi-height observational data. We obtained temperature, density and magnetic field estimates from the GREGOR High-resolution Fast Imager (HiFI), and Infrared Spectrograph (GRIS), IRIS, EIS and complementary data from SDO/AIA. Using observational data and models (e.g., FALC and PFSS), we determined the plasma $\beta$ in the photosphere, chromosphere, transition region and corona. The obtained plasma $\beta$ values lie inside the expected ranges through the solar atmosphere. However, at EIS and AIA coronal heights (from $1.03\ R_{\odot}$ to $1.20\ R_{\odot}$) plasma $\beta$ values appear in the limit defined by Gary (2001); such behavior was previously reported by Rodr\'iguez G\'omez et al. (2019). Additionally, we obtained the plasma $\beta$ in the solar photosphere at different optical depths from $\log\ \tau=-1.0$ to $\log\ \tau=-2.0$. These values decrease with optical depth. This work provides a complete picture of plasma $\beta$ in quiet sun regions through the solar atmosphere, which is a pre-requisite of a better understanding of the plasma dynamics at the base of the solar corona.