Non-equilibrium thermodynamics in the soalr atmosphere and interior.

This article focuses on recent advances and ongoing challenges in understanding thermal regulation in the Sun’s atmosphere, particularly addressing the coronal heating problem and related dynamic processes. It highlights new observational and theoretical insights into phenomena such as coronal rain, chromospheric evaporation, and magnetohydrodynamic (MHD) waves, emphasizing the role of thermal misbalance, thermal instabilities—including a newly identified catastrophic cooling instability—and non-local thermal transport effects. The article also discusses improved diagnostic methods like the Response Fit (RFit) technique for separating hot and cold plasma emissions, the impact of partial ionization in the chromosphere, and the importance of incorporating non-adiabatic effects in helio- and asteroseismology models. Overall, it underscores the necessity of considering thermal non-equilibrium alongside magnetic and mechanical forces to better understand the Sun’s atmospheric dynamics and energy cycles.