CME Induced Thermodynamic Changes in the Corona as Inferred from Fe XI and Fe XIV Emission Observations during the 2017 August 21 Total Solar Eclipse

TL;DR

This study used multi-site eclipse observations to measure how a CME affected the thermodynamic properties of the solar corona, revealing temperature changes between 1.1 and 1.4 million Kelvin in different regions.

Contribution

First remote sensing measurements of CME impact on coronal thermodynamics between 1 and 3 solar radii using Fe XI and Fe XIV emission lines during a total solar eclipse.

Findings

CME activity caused significant temperature changes in the corona.

Coronal hole temperatures ranged from 1.1 to 1.2 million K.

Streamer temperatures ranged from 1.2 to 1.4 million K.

Abstract

We present the first remote sensing observations of the impact from a Coronal Mass Ejection (CME) on the thermodynamic properties of the solar corona between 1 and 3 Rs. Measurements of the Fe XI (789.2 nm) and Fe XIV (530.3 nm) emission were acquired with identical narrow-bandpass imagers at three observing sites during the 2017 August 21 Total Solar Eclipse. Additional continuum imagers were used to observe K+F corona scattering, which is critical for the diagnostics presented here. The total distance between sites along the path of totality was 1400 km, corresponding to a difference of 28 minutes between the times of totality at the first and last site. These observations were used to measure the Fe XI and Fe XIV emission relative to continuum scattering, as well as the relative abundance of Fe 10+ and Fe 13+ from the line ratio. The electron temperature (Te) was then computed via theoretical ionization abundance values. We find that the range of Te is 1.1-1.2 x10^6 K in coronal holes and 1.2-1.4 x10^6 K in streamers. Statistically significant changes of Te occurred throughout much of the corona between the sites as a result of serendipitous CME activity prior to the eclipse. These results underscore the unique advantage of multi-site and multi-wavelength total solar eclipse observations for probing the dynamic and thermodynamic properties of the corona over an uninterrupted distance range from 1 to 3 Rs.