Hot coronal loops associated with umbral brightenings

TL;DR

This study investigates umbral brightenings and associated hot coronal loops using multi-wavelength solar observations, revealing impulsively heated loops cooling over time with plasma temperatures around 6.5 million Kelvin.

Contribution

It provides new observational evidence of hot coronal loops linked to umbral brightenings, including their temperature evolution and magnetic connectivity.

Findings

Detection of umbral brightenings in multiple wavelengths.

Identification of hot coronal loops connecting brightenings to opposite polarity regions.

Plasma temperature around 6.5 million Kelvin indicating impulsive heating and cooling.

Abstract

We analyzed AIA/SDO high-cadence images in all bands, HMI/SDO data, soft X-ray images from SXI/GOES-15, and Halpha images from the GONG network. We detected umbral brightenings that were visible in all AIA bands as well as in Halpha. Moreover, we identified hot coronal loops that connected the brightenings with nearby regions of opposite magnetic polarity. These loops were initially visible in the 94 A band, subsequently in the 335 A band, and in one case in the 211 A band. A differential emission measure analysis revealed plasma with an average temperature of about 6.5x10^6 K. This behavior suggests cooling of impulsively heated loops.