When hot meets cold: post-flare coronal rain

Abstract

Most solar flares demonstrate a prolonged, hourlong post-flare (or gradual) phase, characterized by arcade-like, post-flare loops (PFLs) visible in many extreme ultraviolet (EUV) passbands. These coronal loops are filled with hot -- $\sim 30\mathrm{MK}$ -- and dense plasma, evaporated from the chromosphere during the impulsive phase of the flare, and they very gradually recover to normal coronal density and temperature conditions. During this gradual cooling down to $\sim 1\mathrm{MK}$ regimes, much cooler -- $\sim 0.01\mathrm{MK}$ -- and denser coronal rain is frequently observed inside PFLs. Understanding PFL dynamics in this long-duration, gradual phase is crucial to the entire corona-chromosphere mass and energy cycle. Here we report a simulation in which a solar flare evolves from pre-flare, over impulsive phase all the way into its gradual phase, which successfully reproduces post-flare coronal rain. This rain results from catastrophic cooling caused by thermal instability, and we analyse the entire mass and energy budget evolution driving this sudden condensation phenomenon. We find that the runaway cooling and rain formation also induces the appearance of dark post-flare loop systems, as observed in EUV channels. We confirm and augment earlier observational findings, suggesting that thermal conduction and radiative losses alternately dominate the cooling of PFLs.

accepted by ApJL

References in corpus (26)

• CHIANTI - An atomic database for Emission Lines. Version 8
• MPI-AMRVAC 2.0 for Solar and Astrophysical Applications
• A new radiative cooling curve based on an up to date plasma emission code
• Observing the fine structure of loops through high resolution spectroscopic observations of coronal rain with the CRISP instrument at the Swedish Solar Telescope
• The multi-thermal and multi-stranded nature of coronal rain
• Unprecedented Fine Structure of a Solar Flare Revealed by the 1.6~m New Solar Telescope
• Multidimensional modeling of coronal rain dynamics
• Magnetohydrodynamic shocks in and above post-flare loops: two-dimensional simulation and a simplified model
• Coronal rain in magnetic arcades: Rebound shocks, Limit cycles, and Shear flows
• Simulations of solar filament fine structures and their counterstreaming flows
• Unresolved fine-scale structure in solar coronal loop-tops
• A fully self-consistent model for solar flares
• Coronal rain in magnetic bipolar weak fields
• Observing the formation of flare-driven coronal rain
• Thermal instabilities: Fragmentation and field misalignment of filament fine structure
• Modelling of Reflective Propagating Slow-mode Wave in a Flaring Loop
• Simulating coronal condensation dynamics in 3D
• High-Density Off-Limb Flare Loops Observed by SDO
• Chromospheric and Coronal Observations of Solar Flares with the Helioseismic and Magnetic Imager
• Transition region adaptive conduction (TRAC) in multidimensional magnetohydrodynamic simulations
• The Cooling of Coronal Plasmas. iv: Catastrophic Cooling of Loops
• Self-consistent 3D radiative MHD simulations of coronal rain formation and evolution
• Electron Beams Cannot Directly Produce Coronal Rain
• Soft X-ray emission in kink-unstable coronal loops
• Dark Post-Flare Loops Observed by Solar Dynamics Observatory
• Signatures of Helium continuum in cool flare loops observed by SDO/AIA

Cited by in corpus (11)

• Coronal rain in randomly heated arcades
• MHD turbulence formation in solar flares: 3D simulation and synthetic observations
• The influence of flux rope heating models on solar prominence formation
• A Superflare on YZ Canis Minoris Observed by Seimei Telescope and TESS: Red Asymmetry of H$\alpha$ Emission Associated with White-Light Emission
• High resolution near-infrared spectroscopy of a flare around the ultracool dwarf vB 10
• To Rain or Not to Rain: Correlating GOES Flare Class and Coronal Rain Statistics
• 3D coupled tearing-thermal evolution in solar current sheets
• Simulating stellar coronal rain and slingshot prominences
• From eruption to post-flare rain: a 2.5D MHD model
• Imaging and Spectroscopic Observations of the Dynamic Processes in Limb Solar Flares
• Coronal rain formation in a two-fluid approximation