High Spatial Resolution Observations of Loops in the Solar Corona

TL;DR

This study uses high-resolution solar observations to measure coronal loop widths, revealing that loops are typically structured at scales of several hundred kilometers, which impacts theories of coronal heating.

Contribution

The paper provides the first direct measurements of coronal loop widths at 200km resolution, showing they peak around 270km, thus constraining models of solar corona structure.

Findings

Loops are typically about 270km wide.

Temperature distributions in loops are very narrow.

Coronal loops are structured at scales above many proposed mechanisms.

Abstract

Understanding how the solar corona is structured is of fundamental importance to determining how the Sun's upper atmosphere is heated to high temperatures. Recent spectroscopic studies have suggested that an instrument with a spatial resolution of 200km or better is necessary to resolve coronal loops. The High Resolution Coronal Imager (Hi-C) achieved this performance on a rocket flight in July 2012. We use Hi-C data to measure the Gaussian widths of 91 loops observed in the solar corona and find a distribution that peaks at about 270km. We also use Atmospheric Imaging Assembly (AIA) data for a subset of these loops and find temperature distributions that are generally very narrow. These observations provide further evidence that loops in the solar corona are often structured at a scale of several hundred kilometers, well above the spatial scale of many proposed physical mechanisms.