The Mechanism for the Energy Buildup Driving Solar Eruptive Events

Abstract

The underlying origin of solar eruptive events (SEEs), ranging from giant coronal mass ejections to small coronal-hole jets, is that the lowest-lying magnetic flux in the Sun's corona undergoes the continual buildup of stress and free energy. This magnetic stress has long been observed as the phenomenon of "filament channels:" strongly sheared magnetic field localized around photospheric polarity inversion lines. However, the mechanism for the stress buildup - the formation of filament channels - is still debated. We present magnetohydrodynamic simulations of a coronal volume that is driven by transient, cellular boundary flows designed to model the processes by which the photosphere drives the corona. The key feature of our simulations is that they accurately preserve magnetic helicity, the topological quantity that is conserved even in the presence of ubiquitous magnetic reconnection. Although small-scale random stress is injected everywhere at the photosphere, driving stochastic reconnection throughout the corona, the net result of the magnetic evolution is a coherent shearing of the lowest-lying field lines. This highly counter-intuitive result - magnetic stress builds up locally rather than spreading out to attain a minimum energy state - explains the formation of filament channels and is the fundamental mechanism underlying SEEs. Furthermore, this mechanism may be relevant to other astrophysical or laboratory plasmas.

arXiv comment14 pages + 4 figures. Submitted to ApJL

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• A Model for Energy Buildup and Eruption Onset in Coronal Mass Ejections
• Power-Law Statistics Of Driven Reconnection In The Magnetically Closed Corona
• Modeling a Coronal Mass Ejection from an Extended Filament Channel. I. Eruption and Early Evolution
• The Role of Twist in Kinked Flux Rope Emergence and Delta-Spot Formation
• The Role of Magnetic Helicity in Coronal Heating
• Determining the Transport of Magnetic Helicity and Free Energy in the Sun's Atmosphere
• STITCH: A Subgrid-Scale Model for Energy Buildup in the Solar Corona
• Formation of Quiescent Prominence Magnetic Field by Supergranulations
• Magnetic field line twisting by photospheric vortices: energy storage and release
• Nanoflare Diagnostics from Magnetohydrodynamic Heating Profiles
• The Dynamic Coupling of Streamers and Pseudostreamers to the Heliosphere
• The Minimal Helicity of Solar Coronal Magnetic Fields
• Role of magnetic shear distribution on the formation of eruptive flux ropes