Coronal magnetic field and the plasma beta determined from radio and multiple satellite observations

Takuya Takahashi,Kazumasa Iwai,Jun Kitagawa,Hirotaka Kashiwagi,Shinpei Sawada,Shun Miyawaki,Kiyoto Shibasaki,Satoshi Nozawa

doi:10.1186/s40623-014-0149-z

Abstract

We derived the coronal magnetic field, plasma density, and temperature from the observation of polarization and intensity of radio thermal free-free emission using the Nobeyama Radioheliograph (NoRH) and extreme ultraviolet (EUV) observations. We observed a post-flare loop on the west limb on 11 April 2013. The line-of-sight magnetic field was derived from the circularly polarized free-free emission observed by NoRH. The emission measure and temperature were derived from the Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO). The derived temperature was used to estimate the emission measure from the NoRH radio free-free emission observations. The derived density from NoRH was larger than that determined using AIA, which can be explained by the fact that the low-temperature plasma is not within the temperature coverage of the AIA filters used in this study. We also discuss the other observation of the post-flare loops by the EUV Imager onboard the Solar Terrestrial Relations Observatory (STEREO), which can be used in future studies to reconstruct the coronal magnetic field strength. The derived plasma parameters and magnetic field were used to derive the plasma beta, which is a ratio between the magnetic pressure and the plasma pressure. The derived plasma beta is about 5.7 × 10−4 to 7.6 × 10−4 at the loop top region.

Highlights

We derived the coronal magnetic field, plasma density, and temperature from the observation of polarization and intensity of radio thermal free-free emission using the Nobeyama Radioheliograph (NoRH) and extreme ultraviolet (EUV) observations
In the solar corona, there exist various dynamical phenomena such as flares and coronal mass ejections (CMEs), which are thought to be caused by the interactions between the coronal magnetic field and plasma
Coronal science usually requires a precise measurement of coronal plasma parameters, such as the magnetic field, plasma density, and temperature, which is usually difficult

Summary

Introduction

We derived the coronal magnetic field, plasma density, and temperature from the observation of polarization and intensity of radio thermal free-free emission using the Nobeyama Radioheliograph (NoRH) and extreme ultraviolet (EUV) observations. The line-of-sight magnetic field was derived from the circularly polarized free-free emission observed by NoRH. The emission measure and temperature were derived from the Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO). The derived temperature was used to estimate the emission measure from the NoRH radio free-free emission observations. We discuss the other observation of the post-flare loops by the EUV Imager onboard the Solar Terrestrial Relations Observatory (STEREO), which can be used in future studies to reconstruct the coronal magnetic field strength. The derived plasma beta is about 5.7 × 10−4 to 7.6 × 10−4 at the loop top region

Objectives

Results

Discussion

Conclusion