Dynamics of braided coronal loops

Wilmot-Smith, A. L.; Pontin, D. I.; Hornig, G.

doi:10.1051/0004-6361/201014041

Cited by 73 publications

(66 citation statements)

References 26 publications

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“…This conclusion agrees with that reached by Zhao et al (2015), who used a much simpler setup with far fewer rotation cells. The fundamental reason that the random convection pattern shows a very similar coronal end state to that of the fixed pattern is that, as shown by numerous simulations, magnetic reconnection is efficient at destroying all higher order topological features such as braiding, leaving only the global helicity (e.g., Wilmot-Smith et al 2010). Our results are fully in agreement with this hypothesis.…”

Section: Implications For Coronal Structuresupporting

confidence: 88%

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The Role of Magnetic Helicity in Structuring the Solar Corona

Knizhnik

Antiochos

DeVore

2017

ApJ

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Two of the most widely observed and yet most puzzling features of the Sun's magnetic field are coronal loops that are smooth and laminar and prominences/filaments that are strongly sheared. These two features would seem to be quite unrelated in that the loops are near their minimumenergy current-free state, whereas filaments are regions of high magnetic stress and intense electric currents. We argue that, in fact, these two features are inextricably linked in that both are due to a single process: the injection of magnetic helicity into the corona by photospheric motions and the subsequent evolution of this helicity by coronal reconnection. In this paper, we present numerical simulations of the response of a Parker (1972) corona to photospheric driving motions that have varying degrees of helicity preference. We obtain four main conclusions: 1) in agreement with the helicity condensation model of Antiochos (2013), the inverse cascade of helicity by magnetic reconnection results in the formation of prominences/filaments localized about polarity inversion lines (PILs); 2) this same process removes most structure from the rest of the corona, resulting in smooth and laminar coronal loops; 3) the amount of remnant tangling in coronal loops is inversely dependent on the net helicity injected by the driving motions; and 4) the structure of the solar corona depends only on the helicity preference of the driving motions and not on their detailed time dependence. We discuss the implications of our results for high-resolution observations of the corona.

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Section: Implications For Coronal Structuresupporting

confidence: 88%

“…Therefore, we conclude that it is sufficient to model the helicity injection into the corona with simple twisting motions as has been done by many authors (e.g. Wilmot-Smith et al 2010;Rappazzo et al 2013). Such flows have routinely been observed in helioseismic measurements (Duvall & Gizon 2000;Gizon & Duvall 2003;Komm et al 2007;Seligman et al 2014).…”

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confidence: 60%

The Role of Magnetic Helicity in Structuring the Solar Corona

Knizhnik

Antiochos

DeVore

2017

ApJ

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“…Current sheets may also form away from null points (e.g., Titov et al 2002;Browning et al 2008;Wilmot-Smith et al 2010). Models for the local reconnection process here (e.g., Hornig & Priest 2003;Wilmot-Smith et al 2006 show that, just as in the 3D null case, there are many distinct 3D characteristics of reconnection, some of which we discuss below.…”

Section: Introductionmentioning

confidence: 74%

A Time-Dependent Model for Magnetic Reconnection in the Presence of a Separator

Wilmot-Smith

Hornig

2011

ApJ

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We present a model for separator reconnection due to an isolated reconnection process. Separator reconnection is a process which occurs in the neighborhood of a distinguished field line (the separator) connecting two null points of a magnetic field. It is, for example, important for the dynamics of magnetic flux at the dayside magnetopause and in the solar corona. We find that, above a certain threshold, such a reconnection process generates new separators, which leads to a complex system of magnetic flux tubes connecting regions of previously separated flux. Our findings are consistent with the findings of large numbers of separators in numerical simulations. We discuss how to measure and interpret the reconnection rate in a configuration with multiple separators.

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“…The basic properties of the resistive relaxation of E 3 have been described in Wilmot-Smith et al (2010) and Pontin et al (2011). The braided field is found to be unstable (although the precise nature of the instability is yet to be determined) and in the early stages of the resistive evolution two main thin current layers are formed in the central regions of the domain.…”

Section: Resultsmentioning

confidence: 99%

Heating of braided coronal loops

Wilmot-Smith

Pontin

Yeates

et al. 2011

A&A

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Aims. We investigate the relaxation of braided magnetic loops in order to find out how the type of braiding via footpoint motions affects resultant heating of the loop. Methods. Two magnetic loops, braided in different ways, are used as initial conditions in resistive MHD simulations and their subsequent evolution is studied. Results. The fields both undergo a resistive relaxation in which current sheets form and fragment and the system evolves towards a state of lower energy. In one case this relaxation is very efficient with current sheets filling the volume and homogeneous heating of the loop occurring. In the other case fewer current sheets develop, less magnetic energy is released in the process and a patchy heating of the loop results. The two cases, although very similar in their setup, can be distinguished by the mixing properties of the photospheric driver. The mixing can be measured by the topological entropy of the plasma flow, an observable quantity.

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Dynamics of braided coronal loops

Cited by 73 publications

References 26 publications

The Role of Magnetic Helicity in Structuring the Solar Corona

The Role of Magnetic Helicity in Structuring the Solar Corona

A Time-Dependent Model for Magnetic Reconnection in the Presence of a Separator

Heating of braided coronal loops

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