Beyond small-scale transients: a closer look at the diffuse quiet solar corona

TL;DR

This study investigates the diffuse quiet solar corona at 1 MK, revealing its lack of spatial structuring and small intensity fluctuations, contrasting it with dynamic coronal features like bright points, and exploring potential energization mechanisms.

Contribution

The paper provides a detailed high-resolution analysis of the diffuse quiet Sun corona, highlighting its persistent lack of structure and small fluctuations, and discusses possible underlying physical processes.

Findings

Diffuse corona lacks visible structuring over 25 minutes.

Intensity fluctuations are within +/-5%, smaller than bright points.

Total intensity of diffuse corona is comparable to bright points.

Abstract

Within the quiet Sun corona imaged at 1 MK, much of the field of view consists of diffuse emission that appears to lack the spatial structuring that is so evident in coronal loops or bright points. We seek to determine if these diffuse regions are categorically different in terms of their intensity fluctuations and spatial configuration from the more well-studied dynamic coronal features. We analyze a time series of observations from Solar Orbiter's High Resolution Imager in the Extreme Ultraviolet to quantify the characterization of the diffuse corona at high spatial and temporal resolutions. We then compare this to the dynamic features within the field of view, mainly a coronal bright point. We find that the diffuse corona lacks visible structuring, such as small embedded loops, and that this is persistent over the 25 min duration of the observation. The intensity fluctuations of the diffuse corona, which are within +/-5%, are significantly smaller in comparison to the coronal bright point. Yet, the total intensity observed in the diffuse corona is of the same order as the bright point. It seems inconsistent with our data that the diffuse corona is a composition of small loops or jets or that it is driven by discrete small heating events that follow a power-law-like distribution. We speculate that small-scale processes like MHD turbulence might be energizing the diffuse regions, but at this point we cannot offer a conclusive explanation for the nature of this feature.