Formation of coronal rain triggered by impulsive heating associated with magnetic reconnection

Kohutova, Petra; Verwichte, E.; Froment, C.

doi:10.1051/0004-6361/201936253

Cited by 18 publications

(14 citation statements)

References 52 publications

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“…In this scenario, interchange reconnection between open and closed loops is invoked to explain the presence of coronal rain within the closed loops, although it is yet unclear if reconnection itself plays a direct role in the generation of coronal rain. This seems indeed possible, as suggested by IRIS observations from Kohutova, Verwichte, and Froment (2019).…”

Section: Coronal Rainmentioning

confidence: 61%

A New View of the Solar Interface Region from the Interface Region Imaging Spectrograph (IRIS)

et al. 2021

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The Interface Region Imaging Spectrograph (IRIS) has been obtaining near- and far-ultraviolet images and spectra of the solar atmosphere since July 2013. IRIS is the highest resolution observatory to provide seamless coverage of spectra and images from the photosphere into the low corona. The unique combination of near- and far-ultraviolet spectra and images at sub-arcsecond resolution and high cadence allows the tracing of mass and energy through the critical interface between the surface and the corona or solar wind. IRIS has enabled research into the fundamental physical processes thought to play a role in the low solar atmosphere such as ion–neutral interactions, magnetic reconnection, the generation, propagation, and dissipation of waves, the acceleration of non-thermal particles, and various small-scale instabilities. IRIS has provided insights into a wide range of phenomena including the discovery of non-thermal particles in coronal nano-flares, the formation and impact of spicules and other jets, resonant absorption and dissipation of Alfvénic waves, energy release and jet-like dynamics associated with braiding of magnetic-field lines, the role of turbulence and the tearing-mode instability in reconnection, the contribution of waves, turbulence, and non-thermal particles in the energy deposition during flares and smaller-scale events such as UV bursts, and the role of flux ropes and various other mechanisms in triggering and driving CMEs. IRIS observations have also been used to elucidate the physical mechanisms driving the solar irradiance that impacts Earth’s upper atmosphere, and the connections between solar and stellar physics. Advances in numerical modeling, inversion codes, and machine-learning techniques have played a key role. With the advent of exciting new instrumentation both on the ground, e.g. the Daniel K. Inouye Solar Telescope (DKIST) and the Atacama Large Millimeter/submillimeter Array (ALMA), and space-based, e.g. the Parker Solar Probe and the Solar Orbiter, we aim to review new insights based on IRIS observations or related modeling, and highlight some of the outstanding challenges.

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Section: Coronal Rainmentioning

confidence: 61%

A New View of the Solar Interface Region from the Interface Region Imaging Spectrograph (IRIS)

et al. 2021

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“…This IRIS dataset has been previously analysed by Kohutova et al (2019) and Schad (2018) with a focus on coronal rain. In particular, Kohutova et al (2019) performed a detailed analysis of the reconnection event, the onset of thermal instability and associated coronal rain formation in one of the coronal loops. The analysis therein however excluded the upward-moving surge material and the associated downflows.…”

Section: Observationmentioning

confidence: 99%

First direct observation of a torsional Alfvén oscillation at coronal heights

Kohutova

Verwichte

Froment

2020

A&A

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Context. Torsional Alfvén waves are promising candidates for transport of energy across different layers of the solar atmosphere and have been theoretically predicted for decades. Previous detections of Alfvén waves so far have however mostly relied on indirect signatures. Aims. We present a first direct observational evidence of a fully resolved torsional Alfvén oscillation of a large-scale structure occurring at coronal heights. Methods. We analyse IRIS imaging and spectral observation of a surge resulting from magnetic reconnection between active region prominence threads and surrounding magnetic fieldlines. Results. The IRIS spectral data provides clear evidence of an oscillation in the line-of-sight velocity with a 180 • phase difference between the oscillation signatures at opposite edges of the surge flux tube. This together with an alternating tilt in the Si IV and Mg II k spectra across the flux tube and the trajectories traced by the individual threads of the surge material provides clear evidence of torsional oscillation of the flux tube. Conclusions. Our observation shows that magnetic reconnection leads to the generation of large-scale torsional Alfvén waves.

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“…Its quantitative role in the mass cycle and heating of the solar atmosphere has yet to be determined. Recent works have shown that apart from stratified heating in the atmosphere leading to TNE and, thus, evaporation-condensation cycles, other ways may exist to reach this rain-triggering thermal instability: magnetic reconnection between open-structure and low-lying closed loops (Liu et al 2016;Li et al 2018), interchange reconnection in null-point topologies (Mason et al 2019), and reconnection-induced localised heating (Kohutova et al 2019). Due to their recent discovery, the details of the mechanisms that take place in such configurations are currently unclear.…”

Section: Contextmentioning

confidence: 99%

Multi-scale observations of thermal non-equilibrium cycles in coronal loops

Froment

Antolin

Henriques

et al. 2019

A&A

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Context. Thermal non-equilibrium (TNE) is a phenomenon that can occur in solar coronal loops when the heating is quasi-constant and highly-stratified. Under such heating conditions, coronal loops undergo cycles of evaporation and condensation. The recent observations of ubiquitous long-period intensity pulsations in coronal loops and their relationship with coronal rain have demonstrated that understanding the characteristics of TNE cycles is an essential step in constraining the circulation of mass and energy in the corona. Aims. We report unique observations with the Solar Dynamics Observatory (SDO) and the Swedish 1-m Solar Telescope (SST) that link the captured thermal properties across the extreme spatiotemporal scales covered by TNE processes. Methods. Within the same coronal loop bundle, we captured 6 hr period coronal intensity pulsations in SDO/AIA and coronal rain observed off-limb in the chromospheric Hα and Ca II K spectral lines with SST/CRISP and SST/CHROMIS. We combined a multithermal analysis of the cycles with AIA and an extensive spectral characterisation of the rain clumps with the SST. Results. We find clear evidence of evaporation-condensation cycles in the corona which are linked with periodic coronal rain showers. The high-resolution spectroscopic instruments at the SST reveal the fine-structured rain strands and allow us to probe the cooling phase of one of the cycles down to chromospheric temperatures. Conclusions. These observations reinforce the link between long-period intensity pulsations and coronal rain. They also demonstrate the capability of TNE to shape the dynamics of active regions on the large scales as well as on the smallest scales currently resolvable.

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Formation of coronal rain triggered by impulsive heating associated with magnetic reconnection

Cited by 18 publications

References 52 publications

A New View of the Solar Interface Region from the Interface Region Imaging Spectrograph (IRIS)

A New View of the Solar Interface Region from the Interface Region Imaging Spectrograph (IRIS)

First direct observation of a torsional Alfvén oscillation at coronal heights

Multi-scale observations of thermal non-equilibrium cycles in coronal loops

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