Emission Measure Distribution for Diffuse Regions in Solar Active Regions

TL;DR

This study investigates the thermal structure of diffuse regions around solar active regions using spectral data, revealing evidence of both low and high frequency nanoflare heating events affecting their emission measure distribution.

Contribution

It provides new insights into the heating mechanisms of diffuse solar active region regions through detailed spectral analysis and emission measure distribution characterization.

Findings

EM peaks at log T = 6.25

Cool-ward slopes range from 1.4 to 3.3

Evidence of both low and high frequency nanoflare heating

Abstract

Our knowledge of the diffuse emission that encompasses active regions is very limited. In the present paper we investigate two off-limb active regions, namely AR10939 and AR10961, to probe the underlying heating mechanisms. For this purpose we have used spectral observations from Hinode/EIS and employed the emission measure (EM) technique to obtain the thermal structure of these diffuse regions. Our results show that the characteristic EM distributions of the diffuse emission regions peak at log T = 6.25 and the cool-ward slopes are in the range 1.4 - 3.3. This suggests that both low as well as high frequency nanoflare heating events are at work. Our results provide additional constraints on the properties of these diffuse emission regions and their contribution to the background/foreground when active region cores are observed on-disk.