How Common are Hot Magnetic Flux Ropes in the Low Solar Corona? A Statistical Study of EUV Observations

TL;DR

This study statistically assesses the frequency of hot magnetic flux ropes in large solar flares using EUV observations, finding they occur in about one-third of events, especially in eruptive flares, with some limitations in detection.

Contribution

It provides the first comprehensive statistical analysis of hot flux ropes in large solar flares using multi-wavelength EUV data, highlighting their prevalence and association with eruptions.

Findings

Hot flux ropes are present in 32% of large flares.

Nearly half of eruptive flares involve hot flux ropes.

The actual occurrence rate may be higher due to observational limitations.

Abstract

We use data at 131, 171, and 304 A from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) to search for hot flux ropes in 141 M-class and X-class solar flares that occurred at solar longitudes equal to or larger than 50 degrees. Half of the flares were associated with coronal mass ejections (CMEs). The goal of our survey is to assess the frequency of hot flux ropes in large flares irrespective of their formation time relative to the onset of eruptions. The flux ropes were identified in 131 A images using morphological criteria and their high temperatures were confirmed by their absence in the cooler 171 and 304 A passbands. We found hot flux ropes in 45 of our events (32% of the flares); 11 of them were associated with confined flares while the remaining 34 were associated with eruptive flares. Therefore almost half (49%) of the eruptive events involved a hot flux rope configuration. The use of supplementary Hinode X-Ray Telescope (XRT) data indicates that these percentages should be considered as lower limits of the actual rates of occurrence of hot flux ropes in large flares.