The coronal energy input from magnetic braiding

Abstract

We estimate the energy input into the solar corona from photospheric footpoint motions, using observations of a plage region by the Hinode Solar Optical Telescope. Assuming a perfectly ideal coronal evolution, two alternative lower bounds for the Poynting flux are computed based on field line footpoint trajectories, without requiring horizontal magnetic field data. When applied to the observed velocities, a bound based solely on displacements between the two footpoints of each field line is tighter than a bound based on relative twist between field lines. Depending on the assumed length of coronal magnetic field lines, the higher bound is found to be reasonably tight compared with a Poynting flux estimate using an available vector magnetogram. It is also close to the energy input required to explain conductive and radiative losses in the active region corona. Based on similar analysis of a numerical convection simulation, we suggest that observations with higher spatial resolution are likely to bring the bound based on relative twist closer to the first bound, but not to increase the first bound substantially. Finally, we put an approximate upper bound on the magnetic energy by constructing a hypothetical ``unrelaxed'' magnetic field with the correct field line connectivity.

10 pages, 11 figures, accepted in Astronomy & Astrophysics

References in corpus (12)

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• On Solving the Coronal Heating Problem
• Non-linear force-free field modeling of a solar active region around the time of a major flare and coronal mass ejection
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• Nonlinear Dynamics of the Parker Scenario for Coronal Heating
• The Sun's Supergranulation
• Intermittent heating in the solar corona employing a 3D MHD model
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• Flare Ribbons Observed with G-band and FeI 6302A Filters of the Solar Optical Telescope on Board Hinode
• Heating of braided coronal loops
• Lagrangian coherent structures in photospheric flows and their implications for coronal magnetic structure
• Decorrelation Times of Photospheric Fields and Flows

Cited by in corpus (8)

• A Comprehensive Radiative Magnetohydrodynamics Simulation of Active Region Scale Flux Emergence from the Convection Zone to the Corona
• The Photospheric Poynting Flux and Coronal Heating
• Braided magnetic fields: equilibria, relaxation and heating
• The Structure and Origin of Switchbacks: Parker Solar Probe Observations
• The importance of horizontal Poynting flux in the solar photosphere
• Helical Twisting Number and Braiding Linkage Number of Solar Coronal Loops
• Dependence of Coronal Loop Heating on the Characteristics of Slow Photospheric Motions
• Topological and statistical properties of nonlinear force-free fields