Understanding Heating in Active Region Cores through Machine Learning. I. Numerical Modeling and Predicted Observables

Barnes, Will T.; Bradshaw, S. J.; Viall, N. M.

doi:10.3847/1538-4357/ab290c

Cited by 23 publications

(13 citation statements)

References 106 publications

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“…We suggest, therefore, that the use of the 171-131 time lag information needs to be revisited and that 304 should be added in time-lag analyses. This is generally not the case even if the timelag map method is now widely used (Viall & Klimchuk 2017;Winebarger et al 2018;Barnes et al 2019).…”

Section: On the Use Of Time-lag Analysis With The 171-131 Channel Pairmentioning

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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Section: On the Use Of Time-lag Analysis With The 171-131 Channel Pairmentioning

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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“…Analysis of EM(T) slopes from coronal observations of active regions (ARs) are generally compatible with high frequency coronal heating (e.g., Warren et al 2012;Del Zanna et al 2015b), though lowfrequency heating is found to also play a role depending on the evolutionary stage of the AR (e.g., Ugarte-Urra & Warren 2012). Additional diagnostics of coronal heating properties are provided for instance by the analysis of time lags imaging observations of AR in different passbands sensitive to different temperature (e.g., Viall & Klimchuk 2011;Winebarger et al 2018; Barnes et al 2019) with the Atmospheric Imaging Assembly (AIA, Lemen et al 2012) onboard the Solar Dynamics Observatory (SDO; Pesnell et al 2012). Studies of elemental abundances in ARs at different evolutionary stages (Baker et al 2015(Baker et al , 2018, or during impulsive heating events (e.g., Warren et al 2016) can also provide clues about heating properties, since the coronal abundances appear to vary with respect to photospheric abundances and this fractionation process is likely related to the heating process (e.g., Feldman 1992;Testa 2010;Testa et al 2015).…”

Section: Introductionmentioning

confidence: 99%

IRIS Observations of Short-term Variability in Moss Associated with Transient Hot Coronal Loops

Testa

Polito

Pontieu

2020

ApJ

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We observed rapid variability ( 60 s) at the footpoints of transient hot (∼ 8 − 10 MK) coronal loops in active region cores, with the Interface Region Imaging Spectrograph (IRIS). The high spatial (∼ 0.33 ) and temporal ( 5-10 s) resolution is often crucial for the detection of this variability. We show how, in combination with 1D RADYN loop modeling, these IRIS spectral observations of the transition region (TR) and chromosphere provide powerful diagnostics of the properties of coronal heating and energy transport (thermal conduction and/or non-thermal electrons (NTE)). Our simulations of nanoflare heated loops indicate that emission in the Mg ii triplet can be used as a sensitive diagnostic for non-thermal particles. In our events we observe a large variety of IRIS spectral properties (intensity, Doppler shifts, broadening, chromospheric/TR line ratios, Mg ii triplet emission) even for different footpoints of the same coronal events. In several events, we find spectroscopic evidence for NTE (e.g., TR blue-shifts and Mg ii triplet emission) suggesting that particle acceleration can occur even for very small magnetic reconnection events which are generally below the detection threshold of hard X-ray instruments that provide direct detection of emission of non-thermal particles.

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“…Therefore, for studies of multiple loops forming an active region (Bradshaw & Viall 2016;Barnes et al 2019) and for long simulations Winebarger et al 2018), it is desirable to develop methods that mitigate the need for highly resolved numerical grids. Further, there is Article number, page 1 of 20 arXiv:2002.01887v2 [astro-ph.SR] 28 Feb 2020 also a need for a 1D code that can be run quickly in order to assess the viability of physical ideas.…”

Section: Introductionmentioning

confidence: 99%

Modelling the solar transition region using an adaptive conduction method

Johnston

Cargill

Hood

et al. 2020

A&A

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Modelling the solar Transition Region with the use of an Adaptive Conduction (TRAC) method permits fast and accurate numerical solutions of the field-aligned hydrodynamic equations, capturing the enthalpy exchange between the corona and transition region, when the corona undergoes impulsive heating. The TRAC method eliminates the need for highly resolved numerical grids in the transition region and the commensurate very short time steps that are required for numerical stability. When employed with coarse spatial resolutions, typically achieved in multi-dimensional magnetohydrodynamic codes, the errors at peak density are less than 5% and the computation time is three orders of magnitude faster than fully resolved field-aligned models. This paper presents further examples that demonstrate the versatility and robustness of the method over a range of heating events, including impulsive and quasi-steady footpoint heating. A detailed analytical assessment of the TRAC method is also presented, showing that the approach works through all phases of an impulsive heating event because (i) the total radiative losses and (ii) the total heating when integrated over the transition region are both preserved at all temperatures under the broadening modifications of the method. The results from the numerical simulations complement this conclusion.

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Understanding Heating in Active Region Cores through Machine Learning. I. Numerical Modeling and Predicted Observables

Cited by 23 publications

References 106 publications

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

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

IRIS Observations of Short-term Variability in Moss Associated with Transient Hot Coronal Loops

Modelling the solar transition region using an adaptive conduction method

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