A solar flare driven by thermal conduction observed in mid-infrared

Abstract

Context. The mid-infrared (mid-IR) range has been mostly unexplored for the investigation of solar flares. It is only recently that new mid-IR flare observations have begun opening a new window into the response and evolution of the solar chromosphere. These new observations have been mostly performed by the AR30T and BR30T telescopes that are operating in Argentina and Brazil, respectively. Aims. We present the analysis of SOL2019-05-15T19:24, a GOES class C2.0 solar flare observed at 30 THz (10 μm) by the ground-based telescope AR30T. Our aim is to characterize the evolution of the flaring atmosphere and the energy transport mechanism in the context of mid-IR emission. Methods. We performed a multi-wavelength analysis of the event by complementing the mid-IR data with diverse ground- and space-based data from the Solar Dynamics Observatory (SDO), the H-α Solar Telescope for Argentina, and the Expanded Owens Valley Solar Array (EOVSA). Our study includes the analysis of the magnetic field evolution of the flaring region and of the development of the flare. Results. The mid-IR images from AR30T show two bright and compact flare sources that are spatially associated with the flare kernels observed in ultraviolet (UV) by SDO. We confirm that the temporal association between mid-IR and UV fluxes previously reported for strong flares is also observed for this small flare. The EOVSA microwave data revealed flare spectra consistent with thermal free-free emission, which lead us to dismiss the existence of a significant number of non-thermal electrons. We thus consider thermal conduction as the primary mechanism responsible for energy transport. Our estimates for the thermal conduction energy and total radiated energy fall within the same order of magnitude, reinforcing our conclusions.

Multi-Scale Variability of Coronal Loops Set by Thermal Non-Equilibrium and Instability as a Probe for Coronal Heating

“…However, the simulated flare is only of B class, and therefore it is yet unclear how the electron beam, thermal conduction and multi-dimensional effects combine in generating the rain. It is worth to note that recent observations have shown that some flares can be mainly powered by thermal conduction (López et al, 2022).…”

Understanding the Duration of Solar and Stellar Flares at Various Wavelengths

“…Additionally, we have only considered heating due to an electron beam, known to deliver significant amounts of heating to the chromosphere (Emslie et al 2012), but by no means the only mechanism of energy transport. Other potential mechanisms are less well constrained, but likely include direct energy transport via thermal conduction (e.g., López et al 2022), wave generation of MHD waves (e.g., Emslie & Sturrock 1982;Reep & Russell 2016), and acceleration of ion beams (e.g., Canfield & Chang 1985;Kerr et al 2023). Future work with a multithreaded model of flares should attempt to better constrain these mechanisms and their direct role in energy transport over the course of an event.…”

Daytime Sky Quality at El Leoncito, Argentina

“…On the other hand, OAFA hosts the Mirror Coronagraph for Argentina (MICA, see Sect. 2.3), the H-alpha Solar Telescope for Argentina (HASTA, Francile et al, 2008Francile et al, , 2016, the 30-THz solar telescope (AR30T, López et al, 2022) and the High Altitude THz Solar Photometer (HATS, Giménez de Castro et al, 2020).…”