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Estimating the Rate of Field Line Braiding in the Solar Corona by Photospheric Flows

Lookup NU author(s): Professor Paul BushbyORCiD



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


In this paper we seek to understand the timescale on which the photospheric motions on the Sun braid coronal magnetic field lines. This is a crucial ingredient for determining the viability of the braiding mechanism for explaining the high temperatures observed in the corona. We study the topological complexity induced in the coronal magnetic field, primarily using plasma motions extracted from magneto-convection simulations. This topological complexity is quantified using the field line winding, finite time topological entropy and passive scalar mixing. With these measures we contrast mixingefficiencies of the magneto-convection simulation, a benchmark flow known as a `blinking vortex', and finally photospheric flows inferred from sequences of observed magnetograms using local correlation tracking. While the highlyresolved magneto-convection simulations induce a strong degree of field line winding and finite time topological entropy, the values obtained from the observations from the plage region are around an order of magnitude smaller.This behavior is carried over to the finite time topological entropy. Nevertheless, the results suggest that the photospheric motions induce complex tangling of the coronal field on a timescale of hours.

Publication metadata

Author(s): Candelaresi S, Pontin D, Yeates A, Bushby P, Hornig G

Publication type: Article

Publication status: Published

Journal: The Astrophysical Journal

Year: 2018

Volume: 864

Issue: 2

Print publication date: 12/09/2018

Online publication date: 12/09/2018

Acceptance date: 25/07/2018

Date deposited: 30/07/2018

ISSN (print): 0004-637X

ISSN (electronic): 1538-4357

Publisher: Institute of Physics Publishing, Inc.


DOI: 10.3847/1538-4357/aad8bc


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