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Title: δ-SUNSPOT FORMATION IN SIMULATION OF ACTIVE-REGION-SCALE FLUX EMERGENCE

Abstract

δ-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. 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 δ-sunspot with a sharp polarity inversion line. The formation of the δ-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, and strong transverse field with highly sheared magnetic and velocity fields at the polarity inversion line (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 δ-spot overlaid by more relaxed fields connecting the two polarities at the two ends.

Authors:
;  [1]
  1. High Altitude Observatory, National Center for Atmospheric Research, 3090 Center Green Drive, Boulder, CO 80301 (United States)
Publication Date:
OSTI Identifier:
22522321
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 806; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPUTERIZED SIMULATION; CONVECTION; EXPANSION; MAGNETIC FLUX; MAGNETOHYDRODYNAMICS; PHOTOSPHERE; POTENTIALS; ROTATION; SHEAR; SOLAR FLARES; SUN; SUNSPOTS; SURFACES; VELOCITY; ZONES

Citation Formats

Fang, Fang, and Fan, Yuhong. δ-SUNSPOT FORMATION IN SIMULATION OF ACTIVE-REGION-SCALE FLUX EMERGENCE. United States: N. p., 2015. Web. doi:10.1088/0004-637X/806/1/79.
Fang, Fang, & Fan, Yuhong. δ-SUNSPOT FORMATION IN SIMULATION OF ACTIVE-REGION-SCALE FLUX EMERGENCE. United States. https://doi.org/10.1088/0004-637X/806/1/79
Fang, Fang, and Fan, Yuhong. 2015. "δ-SUNSPOT FORMATION IN SIMULATION OF ACTIVE-REGION-SCALE FLUX EMERGENCE". United States. https://doi.org/10.1088/0004-637X/806/1/79.
@article{osti_22522321,
title = {δ-SUNSPOT FORMATION IN SIMULATION OF ACTIVE-REGION-SCALE FLUX EMERGENCE},
author = {Fang, Fang and Fan, Yuhong},
abstractNote = {δ-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. 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 δ-sunspot with a sharp polarity inversion line. The formation of the δ-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, and strong transverse field with highly sheared magnetic and velocity fields at the polarity inversion line (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 δ-spot overlaid by more relaxed fields connecting the two polarities at the two ends.},
doi = {10.1088/0004-637X/806/1/79},
url = {https://www.osti.gov/biblio/22522321}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 806,
place = {United States},
year = {Wed Jun 10 00:00:00 EDT 2015},
month = {Wed Jun 10 00:00:00 EDT 2015}
}