Change ratios of magnetic helicity and magnetic free energy during major solar flares

Abstract

Magnetic helicity is an important concept in solar physics, with a number of theoretical statements pointing out the important role of magnetic helicity in solar flares and coronal mass ejections (CMEs). Here we construct a sample of 47 solar flares, which contains 18 no-CME-associated confined flares and 29 CME-associated eruptive flares. We calculate the change ratios of magnetic helicity and magnetic free energy before and after these 47 flares. Our calculations show that the change ratios of magnetic helicity and magnetic free energy show distinct different distributions in confined flares and eruptive flares. The median value of the change ratios of magnetic helicity in confined flares is $-0.8$%, while this number is $-14.5$% for eruptive flares. For the magnetic free energy, the median value of the change ratios is $-4.3$% for confined flares, whereas this number is $-14.6$% for eruptive flares. This statistical result, using observational data, is well consistent with the theoretical understandings that magnetic helicity is approximately conserved in the magnetic reconnection, as shown by confined flares, and the CMEs take away magnetic helicity from the corona, as shown by eruptive flares.

arXiv comment17 pages, 5 figures, 2 tables, accepted for publication in RAA

References in corpus (19)

• Optimization code with weighting function for the reconstruction of coronal magnetic fields
• Preprocessing of vector magnetograph data for a non-linear force-free magnetic field reconstruction
• VFISV: Very Fast Inversion of the Stokes Vector for the Helioseismic and Magnetic Imager
• Tracking Vector Magnetograms with the Magnetic Induction Equation
• Nonlinear force-free modeling of the solar coronal magnetic field
• A Database of Flare Ribbon Properties From Solar Dynamics Observatory I: Reconnection Flux
• Solar Force-free Magnetic Fields
• Magnetic Field Confinement in the Corona: The Role of Magnetic Helicity Accumulation
• Relative magnetic helicity as a diagnostic of solar eruptivity
• The Magnetic Energy - Helicity Diagram of Solar Active Regions
• Testing magnetic helicity conservation in a solar-like active event
• Validation and Benchmarking of a Practical Free Magnetic Energy and Relative Magnetic Helicity Budget Calculation in Solar Magnetic Structures
• The dependence of the helicity bound of force-free magnetic fields on boundary conditions
• On the reliability of magnetic energy and helicity computations based on nonlinear force-free coronal magnetic field models
• Magnetic helicity and energy of emerging solar active regions and their erruptivity
• Evolution of Relative Magnetic Helicity: New Boundary Conditions for the Vector Potential
• Magnetic Helicity of Self-Similar Axisymmetric Force-free Fields
• On estimating the force-freeness based on observed magnetograms
• Effects of non-radial magnetic field on measuring magnetic helicity transport across solar photosphere

Cited by in corpus (1)

• The Properties of Non-Potential Magnetic Field Parameters in a Super-Active Region with Complex Structures and Strong Solar Flares