$\delta$-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 (7)

• Evolution of Magnetic Field and Energy in A Major Eruptive Active Region Based on SDO/HMI Observation
• A simulation of convective dynamo in the solar convective envelope: maintenance of the solar-like differential rotation and emerging flux
• Numerical simulations of active region scale flux emergence: From spot formation to decay
• Buoyant Magnetic Loops in a Global Dynamo Simulation of a Young Sun
• Formation of a Flare-Productive Active Region: Observation and Numerical Simulation of NOAA AR 11158
• Buildup of Magnetic Shear and Free Energy During Flux Emergence and Cancellation
• Dynamic Coupling of Convective Flows and Magnetic Field during Flux Emergence

Cited by in corpus (21)

• Flare-productive active regions
• Magnetic Properties of Solar Active Regions that Govern Large Solar Flares and Eruptions
• Decoding the Pre-Eruptive Magnetic Field Configurations of Coronal Mass Ejections
• The Origin of Major Solar Activity - Collisional Shearing Between Nonconjugated Polarities of Multiple Bipoles Emerging Within Active Regions
• The Magnetic Classification of Solar Active Regions 1992 - 2015
• Numerical Simulations of Flare-productive Active Regions: delta-sunspots, Sheared Polarity Inversion Lines, Energy Storage, and Predictions
• Numerical Study on Emergence of Kinked Flux Tube for Understanding of Possible Origin of Delta-spot Regions
• 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
• The Role of Twist in Kinked Flux Rope Emergence and Delta-Spot Formation
• 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
• Modeling Repeatedly Flaring $\delta$ Sunspots
• The chromosphere above a $\delta$-sunspot in the presence of fan-shaped jets
• Eruptions and Flaring Activity in Emerging Quadrupolar Regions
• 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