skip to main content

SciTech ConnectSciTech Connect

Title: DISTRIBUTION OF ELECTRIC CURRENTS IN SOLAR ACTIVE REGIONS

There has been a long-standing debate on the question of whether or not electric currents in solar active regions are neutralized. That is, whether or not the main (or direct) coronal currents connecting the active region polarities are surrounded by shielding (or return) currents of equal total value and opposite direction. Both theory and observations are not yet fully conclusive regarding this question, and numerical simulations have, surprisingly, barely been used to address it. Here we quantify the evolution of electric currents during the formation of a bipolar active region by considering a three-dimensional magnetohydrodynamic simulation of the emergence of a sub-photospheric, current-neutralized magnetic flux rope into the solar atmosphere. We find that a strong deviation from current neutralization develops simultaneously with the onset of significant flux emergence into the corona, accompanied by the development of substantial magnetic shear along the active region's polarity inversion line. After the region has formed and flux emergence has ceased, the strong magnetic fields in the region's center are connected solely by direct currents, and the total direct current is several times larger than the total return current. These results suggest that active regions, the main sources of coronal mass ejections and flares, aremore » born with substantial net currents, in agreement with recent observations. Furthermore, they support eruption models that employ pre-eruption magnetic fields containing such currents.« less
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4] ; ;  [5] ;  [6]
  1. Predictive Science, Inc., 9990 Mesa Rim Road, Suite 170, San Diego, CA 92121 (United States)
  2. College of Science, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States)
  3. School of Mathematics and Statistics, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS (United Kingdom)
  4. U.S. Naval Research Lab, 4555 Overlook Avenue, SW Washington, DC 20375 (United States)
  5. LESIA, Observatoire de Paris, CNRS, UPMC, Univ. Paris Diderot, 5 place Jules Janssen, F-92190 Meudon (France)
  6. Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam (Germany)
Publication Date:
OSTI Identifier:
22363994
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 782; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPUTERIZED SIMULATION; DIRECT CURRENT; MAGNETIC FIELDS; MAGNETIC FLUX; MAGNETOHYDRODYNAMICS; MASS; SHEAR; SOLAR ATMOSPHERE; STAR EVOLUTION; SUN; THREE-DIMENSIONAL CALCULATIONS