Catastrophic cooling and cessation of heating in the solar corona

Abstract

Condensations in the more than 10^6 K hot corona of the Sun are commonly observed in the extreme ultraviolet (EUV). While their contribution to the total solar EUV radiation is still a matter of debate, these condensations certainly provide a valuable tool for studying the dynamic response of the corona to the heating processes. We investigate different distributions of energy input in time and space to investigate which process is most relevant for understanding these coronal condensations. For a comparison to observations we synthesize EUV emission from a time-dependent, one-dimensional model for coronal loops, where we employ two heating scenarios: simply shutting down the heating and a model where the heating is very concentrated at the loop footpoints, while keeping the total heat input constant. The heating off/on model does not lead to significant EUV count rates that one observes with SDO/AIA. In contrast, the concentration of the heating near the footpoints leads to thermal non-equilibrium near the loop top resulting in the well-known catastrophic cooling. This process gives a good match to observations of coronal condensations. This shows that the corona needs a steady supply of energy to support the coronal plasma, even during coronal condensations. Otherwise the corona would drain very fast, too fast to even form a condensation.

Astronomy & Astrophysics, in press, 10 pages, 5 figures

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• Intermittent heating in the solar corona employing a 3D MHD model
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• A solar coronal loop in a box: Energy generation and heating
• Limitations of force-free magnetic field extrapolations: revisiting basic assumptions
• Modelling the solar transition region using an adaptive conduction method
• Identifying Observables that can Differentiate Between Impulsive and Footpoint Heating: Time Lags and Intensity Ratios
• EUV fine structure and variability associated with coronal rain revealed by Solar Orbiter/EUI HRIEUV and SPICE
• Heating and cooling of coronal loops observed by SDO
• RATAN-600 Observations of Small Scale Structures with High Spectral Resolution
• Observations and modeling of the emerging EUV loops in the quiet Sun as seen with the Solar Dynamics Observatory
• Synthetic IRIS spectra of the solar transition region: Effect of high-energy tails
• Spatiotemporal Low FIP Abundance: A Catalyst for Coronal Condensation
• Parametrization of coronal heating: spatial distribution and observable consequences
• Heating of quiescent coronal loops caused by nearby eruptions observed with the Solar Dynamics Observatory and the Solar Upper Transition Region Imager
• Magnetic structure of coronal dark halos