$\delta$-Sunspot Formation in Simulation of Active-Region-Scale Flux Emergence

Abstract

$\delta$-sunspots, with highly complex magnetic structures, are very productive in energetic eruptive events, such as X-class flares and homologous eruptions. We here study the formation of such complex magnetic structures by numerical simulations of magnetic flux emergence from the convection zone into the corona in an active-region-scale domain. In our simulation, two pairs of bipolar sunspots form on the surface, originating from two buoyant segments of a single subsurface twisted flux rope, following the approach of Toriumi et al. (2014). Expansion and rotation of the emerging fields in the two bipoles drive the two opposite polarities into each other with apparent rotating motion, producing a compact $\delta$-sunspot with a sharp polarity inversion line. The formation of the $\delta$-sunspot in such a realistic-scale domain produces emerging patterns similar to those formed in observations, e.g. the inverted polarity against Hale's law, the curvilinear motion of the spot, strong transverse field with highly sheared magnetic and velocity fields at the PIL. Strong current builds up at the PIL, giving rise to reconnection, which produces a complex coronal magnetic connectivity with non-potential fields in the Delta-spot overlaid by more relaxed fields connecting the two polarities at the two ends.

References in corpus (2)

• A simulation of convective dynamo in the solar convective envelope: maintenance of the solar-like differential rotation and emerging flux
• Formation of a Flare-Productive Active Region: Observation and Numerical Simulation of NOAA AR 11158

Cited by in corpus (14)

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• Magnetic Properties of Solar Active Regions that Govern Large Solar Flares and Eruptions
• Numerical Simulations of Flare-productive Active Regions: delta-sunspots, Sheared Polarity Inversion Lines, Energy Storage, and Predictions
• Spontaneous Generation of delta-sunspots in Convective Magnetohydrodynamic Simulation of Magnetic Flux Emergence
• A Comprehensive Radiative Magnetohydrodynamics Simulation of Active Region Scale Flux Emergence from the Convection Zone to the Corona
• Filament Eruption and Its Reformation Caused by Emerging Magnetic Flux
• Different contributions to space weather and space climate from different big solar active regions
• A partial filament eruption in three steps induced by external magnetic reconnection
• The chromosphere above a $\delta$-sunspot in the presence of fan-shaped jets
• Flux emergence and generation of flare-productive active regions
• Magnetic Helicity Flux across Solar Active Region Photospheres: II. Association of Hemispheric Sign Preference with Flaring Activity during Solar Cycle 24
• Impact of subsurface convective flows on the formation of sunspot magnetic field and energy build-up
• The configuration and failed eruption of a complex magnetic flux rope above a δ sunspot region
• Magnetohydrodynamics simulation of magnetic flux rope formation in a quadrupolar magnetic field configuration