Impulsive coronal heating during the interaction of surface magnetic fields in the lower solar atmosphere

L P Chitta,S K Solanki,E R Priest,H Peter

doi:10.1051/0004-6361/202039099

Abstract

Coronal plasma in the cores of solar active regions is impulsively heated to more than 5 MK. The nature and location of the magnetic energy source responsible for such impulsive heating is poorly understood. Using observations of seven active regions from the Solar Dynamics Observatory, we found that a majority of coronal loops hosting hot plasma have at least one footpoint rooted in regions of interacting mixed magnetic polarity at the solar surface. In cases when co-temporal observations from the Interface Region Imaging Spectrograph space mission are available, we found spectroscopic evidence for magnetic reconnection at the base of the hot coronal loops. Our analysis suggests that interactions of magnetic patches of opposite polarity at the solar surface and the associated energy release during reconnection are key to impulsive coronal heating.

Highlights

The origin of hot plasma in the solar corona is an open question
Coronal nanoflares produced by tangled magnetic fields are one possible candidate to explain the intermittent heating of plasma to several million degrees Kelvin, in active regions where energy requirements are higher (Parker 1988; Klimchuk 2006; Cirtain et al 2013)
We investigate the magnetic roots of impulsively heated loops in the cores of active regions (ARs), observed with the Solar Dynamics Observatory (SDO; Pesnell et al 2012)

Summary

Introduction

The origin of hot plasma in the solar corona is an open question. On average, the quiescent solar corona requires an energy flux of a few 105 erg cm−2 s−1 to support the radiative and conductive losses, whereas in active regions that host stronger concentrations of magnetic field at the solar surface, the coronal energy requirements are two orders of magnitude higher (Withbroe & Noyes 1977). A widely accepted hypothesis is that coronal magnetic loops become tangled and braided as their footpoints at the solar surface are slowly moved and stressed by photospheric convective motions. Energy stored in these magnetic braids is impulsively and intermittently released through reconnection as coronal nanoflares (Parker 1988). Coronal nanoflares produced by tangled magnetic fields are one possible candidate to explain the intermittent heating of plasma to several million degrees Kelvin, in active regions where energy requirements are higher (Parker 1988; Klimchuk 2006; Cirtain et al 2013)

Objectives

Methods

Conclusion