Observing the formation of flare-driven coronal rain

Abstract

Flare-driven coronal rain can manifest from rapidly cooled plasma condensations near coronal loop-tops in thermally unstable post-flare arcades. We detect 5 phases that characterise the post-flare decay: heating, evaporation, conductive cooling dominance for ~120 s, radiative / enthalpy cooling dominance for ~4700 s and finally catastrophic cooling occurring within 35-124 s leading to rain strands with s periodicity of 55-70 s. We find an excellent agreement between the observations and model predictions of the dominant cooling timescales and the onset of catastrophic cooling. At the rain formation site we detect co-moving, multi-thermal rain clumps that undergo catastrophic cooling from ~1 MK to ~22000 K. During catastrophic cooling the plasma cools at a maximum rate of 22700 K s-1 in multiple loop-top sources. We calculated the density of the EUV plasma from the DEM of the multi-thermal source employing regularised inversion. Assuming a pressure balance, we estimate the density of the chromospheric component of rain to be 9.21x10^11 +-1.76x10^11 cm-3 which is comparable with quiescent coronal rain densities. With up to 8 parallel strands in the EUV loop cross section, we calculate the mass loss rate from the post-flare arcade to be as much as 1.98x10^12 +/-4.95x10^11 g s-1. Finally, we reveal a close proximity between the model predictions of 10^5.8 K and the observed properties between 10^5.9 K and 10^6.2 K, that defines the temperature onset of catastrophic cooling. The close correspondence between the observations and numerical models suggests that indeed acoustic waves (with a sound travel time of 68 s) could play an important role in redistributing energy and sustaining the enthalpy-based radiative cooling.

23 pages, 21 figures

References in corpus (39)

• On Solving the Coronal Heating Problem
• CRISP Spectropolarimetric Imaging of Penumbral Fine Structure
• Differential Emission Measures from the Regularized Inversion of Hinode and SDO data
• Highly Efficient Modeling of Dynamic Coronal Loops
• CRISPRED: A data pipeline for the CRISP imaging spectropolarimeter
• The Dynamic Formation of Prominence Condensations
• Observing the fine structure of loops through high resolution spectroscopic observations of coronal rain with the CRISP instrument at the Swedish Solar Telescope
• Coronal rain as a marker for coronal heating mechanisms
• Solar Corona Loop Studies with AIA: I. Cross-Sectional Temperature Structure
• Flocculent flows in the chromospheric canopy of a sunspot
• RHESSI and SOHO/CDS Observations of Explosive Chromospheric Evaporation
• On active region loops: Hinode/EIS observations
• Evidence for Widespread Cooling in an Active Region Observed with the SDO Atmospheric Imaging Assembly
• Observational Evidence for Gentle Chromospheric Evaporation During the Impulsive Phase of a Solar Flare
• Constraints on the Heating of High Temperature Active Region Loops: Observations from Hinode and SDO
• Diagnostics of stellar flares from X-ray observations: from the decay to the rise phase
• The multi-thermal and multi-stranded nature of coronal rain
• Using a Differential Emission Measure and Density Measurements in an Active Region Core to Test a Steady Heating Model
• Multi-Thread Hydrodynamic Modeling of a Solar Flare
• 3D Temperature Mapping of Solar Photospheric Fine Structure Using Ca II H Filtergrams
• Multidimensional modeling of coronal rain dynamics
• Evidence for evaporation-incomplete condensation cycles in warm solar coronal loops
• The Thermal Properties of Solar Flares Over Three Solar Cycles Using GOES X-ray Observations
• Multi-wavelength observations and modelling of a canonical solar flare
• Generalized Regularization Techniques With Constraints For The Analysis Of Solar Bremsstrahlung X-Ray Spectra
• Static and Dynamic Modeling of a Solar Active Region. I: Soft X-Ray Emission
• Unresolved fine-scale structure in solar coronal loop-tops
• The sub-arcsecond hard X-ray structure of loop footpoints in a solar flare
• Decay Phase Cooling and Inferred Heating of M- and X-class Solar Flares
• How important are electron beams in driving chromospheric evaporation in the 2014 March 29 flare?
• Widespread nanoflare variability detected with Hinode/XRT in a solar active region
• Plasma sloshing in pulse-heated solar and stellar coronal loops
• Signatures of impulsive localized heating in the temperature distribution of multi-stranded coronal loops
• Chromospheric and Coronal Observations of Solar Flares with the Helioseismic and Magnetic Imager
• The Cooling of Coronal Plasmas. iv: Catastrophic Cooling of Loops
• Positions and sizes of X-ray solar flare sources
• The role of radiative losses in the late evolution of pulse-heated coronal loops/strands
• Regularized energy-dependent solar flare hard x-ray spectral index
• Post-flare UV light curves explained with thermal instability of loop plasma

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• On the spectroscopic detection of periodic plasma flows in loops undergoing thermal non-equilibrium
• From Chromospheric Evaporation to Coronal Rain: An Investigation of the Mass and Energy Cycle of a Flare
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• Solar radio burst associated with the falling bright EUV blob
• From eruption to post-flare rain: a 2.5D MHD model
• The Lyman-$\alpha$ Emission in a C1.4 Solar Flare Observed by the Extreme Ultraviolet Imager aboard Solar Orbiter
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