Power-law Statistics of Driven Reconnection in the Magnetically Closed Corona

Knizhnik, K. J.; Uritsky, V. M.; Klimchuk, J. A.; DeVore, C. R.

doi:10.3847/1538-4357/aaa0d9

Cited by 33 publications

(36 citation statements)

References 68 publications

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“…Its Flux Corrected Transport algorithms (DeVore 1991) provide minimal, though finite, numerical dissipation, which allows magnetic reconnection to occur. As a result, ARMS conserves the magnetic helicity in the system to an excellent approximation, even when reconnection occurs throughout a substantial fraction of the total volume (Knizhnik et al 2015;Knizhnik et al 2017a;Knizhnik et al 2017b;Knizhnik et al 2018).…”

Section: Introductionmentioning

confidence: 99%

The Role of Magnetic Helicity in Coronal Heating

Knizhnik

Antiochos

Klimchuk

et al. 2019

ApJ

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One of the greatest challenges in solar physics is understanding the heating of the Sun's corona. Most theories for coronal heating postulate that free energy in the form of magnetic twist/stress is injected by the photosphere into the corona where the free energy is converted into heat either through reconnection or wave dissipation. The magnetic helicity associated with the twist/stress, however, is expected to be conserved and appear in the corona. In previous work we showed that helicity associated with the small-scale twists undergoes an inverse cascade via stochastic reconnection in the corona, and ends up as the observed large-scale shear of filament channels. Our "helicity condensation" model accounts for both the formation of filament channels and the observed smooth, laminar structure of coronal loops. In this paper, we demonstrate, using helicity-and energy-conserving numerical simulations of a coronal system driven by photospheric motions, that the model also provides a natural mechanism for heating the corona. We show that the heat generated by the reconnection responsible for the helicity condensation process is sufficient to account for the observed coronal heating. We study the role that helicity injection plays in determining coronal heating and find that, crucially, the heating rate is only weakly dependent on the net helicity preference of the photospheric driving. Our calculations demonstrate that motions with 100% helicity preference are least efficient at heating the corona; those with 0% preference are most efficient. We discuss the physical origins of this result and its implications for the observed corona.

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Section: Introductionmentioning

confidence: 99%

The Role of Magnetic Helicity in Coronal Heating

Knizhnik

Antiochos

Klimchuk

et al. 2019

ApJ

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“…The kinetic spectral index of ∼0.5 must also be explained. An avalanche-like behavior of reconnection events is one possibility (Knizhnik et al, 2018). We must remember that, because of topological complexities such as separators and QSLs, the velocity pattern in the photosphere-which may be dominated by one scale-is translated into a different velocity pattern in corona, likely involving a range of scales.…”

Section: Discussionmentioning

confidence: 99%

How Turbulent is the Magnetically Closed Corona?

Klimchuk

Antiochos

2021

Front. Astron. Space Sci.

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We argue that the magnetically closed corona evolves primarily quasi-statically, punctuated by many localized bursts of activity associated with magnetic reconnection at a myriad of small current sheets. The sheets form by various processes that do not involve a traditional turbulent cascade whereby energy flows losslessly through a continuum of spatial scales starting from the large scale of the photospheric driving. If such an inertial range is a defining characteristic of turbulence, then the magnetically closed corona is not a turbulent system. It nonetheless has a complex structure that bears no direct relationship to the pattern of driving.

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“…see discussion in; Parnell & De Moortel 2012), and power law distributions of nanoflares can explain the observed range in differential emission measure slopes found in active regions (Cargill 2014). Many theoretical models have also suggested that nanoflares occur with a powerlaw distribution in energy, from a simple cellular automaton (López Fuentes & Klimchuk 2015) to full three dimensional magnetohydrodynamic (MHD) simulations (Knizhnik et al 2018). These models and observational considerations typically find nanoflare energy distributions with power laws of −2.5 α −1.5.…”

Section: Power Law Slopes Of Event Delaysmentioning

confidence: 99%

Transition region contribution to AIA observations in the context of coronal heating

Schonfeld,

Klimchuk

2020

Preprint

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We investigate the relative contributions from the transition region and corona of coronal loops observed by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO). Using EBTEL (Enthalpy-Based Thermal Evolution of Loops) hydrodynamic simulations, we model loops with multiple lengths and energy fluxes heated randomly by events drawn from power-law distributions with different slopes and minimum delays between events to investigate how each of these parameters influences observable loop properties. We generate AIA intensities from the corona and transition region for each realization. The variations within and between models generated with these different parameters illustrate the sensitivity of narrowband imaging to the details of coronal heating.We then analyze the transition region and coronal emission from a number of observed active regions and find broad agreement with the trends in the models. In both models and observations, the transition region brightness is significant, often greater than the coronal brightness in all six "coronal" AIA channels. We also identify an inverse relationship, consistent with heating theories, between the slope of the differential emission measure (DEM) coolward of the peak temperature and the observed ratio of coronal to transition region intensity. These results highlight the use of narrowband observations and the importance of properly considering the transition region in investigations of coronal heating.

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Power-law Statistics of Driven Reconnection in the Magnetically Closed Corona

Cited by 33 publications

References 68 publications

The Role of Magnetic Helicity in Coronal Heating

The Role of Magnetic Helicity in Coronal Heating

How Turbulent is the Magnetically Closed Corona?

Transition region contribution to AIA observations in the context of coronal heating

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