Measuring the Magnetic Field Strength of the Quiet Solar Corona Using "EIT Waves"

TL;DR

This study combines high-cadence imaging and spectroscopic data to measure the magnetic field strength of the quiet solar corona using EIT waves, providing insights into the global magnetic structure of the Sun.

Contribution

It introduces a method to estimate coronal magnetic field strength by integrating pulse kinematics with plasma density measurements from multiple spacecraft.

Findings

Magnetic field strength in the quiet corona is approximately 2-6 G.

EIT waves are influenced by global-scale magnetic fields.

The observed pulse heights agree with PFSS model predictions.

Abstract

Variations in the propagation of globally-propagating disturbances (commonly called "EIT waves") through the low solar corona offer a unique opportunity to probe the plasma parameters of the solar atmosphere. Here, high-cadence observations of two "EIT wave" events taken using the Atmospheric Imaging Assembly (AIA) instrument onboard the Solar Dynamics Observatory (SDO) are combined with spectroscopic measurements from the Extreme ultraviolet Imaging Spectrometer (EIS) onboard the Hinode spacecraft and used to examine the variability of the quiet coronal magnetic-field strength. The combination of pulse kinematics from SDO/AIA and plasma density from Hinode/EIS is used to show that the magnetic-field strength is in the range ~2-6 G in the quiet corona. The magnetic-field estimates are then used to determine the height of the pulse, allowing a direct comparison with theoretical values obtained from magnetic-field measurements from the Helioseismic and Magnetic Imager (HMI) onboard SDO using PFSS and local-domain extrapolations. While local-scale extrapolations predict heights inconsistent with prior measurements, the agreement between observations and the PFSS model indicates that "EIT waves" are a global phenomenon influenced by global-scale magnetic field.