EVIDENCE OF ACTIVE MHD INSTABILITY IN EULAGMHD SIMULATIONS OF SOLAR CONVECTION
Abstract
We investigate the possible development of magnetohydrodynamical instabilities in the EULAGMHD “millennium simulation” of Passos and Charbonneau. This simulation sustains a largescale magnetic cycle characterized by solarlike polarity reversals taking place on a regular multidecadal cadence, and in which zonally oriented bands of strong magnetic fields accumulate below the convective layers, in response to turbulent pumping from above in successive magnetic halfcycles. Key aspects of this simulation include low numerical dissipation and a strongly subadiabatic fluid layer underlying the convectively unstable layers corresponding to the modeled solar convection zone. These properties are conducive to the growth and development of twodimensional instabilities that are otherwise suppressed by stronger dissipation. We find evidence for the action of a nonaxisymmetric magnetoshear instability operating in the upper portions of the stably stratified fluid layers. We also investigate the possibility that the Tayler instability may be contributing to the destabilization of the largescale axisymmetric magnetic component at high latitudes. On the basis of our analyses, we propose a global dynamo scenario whereby the magnetic cycle is driven primarily by turbulent dynamo action in the convecting layers, but MHD instabilities accelerate the dissipation of the magnetic field pumped down into the overshoot and stable layers, thusmore »
 Authors:
 Département de Physique, Université de Montréal, C.P. 6128 Succ. Centreville, Montréal, Qc H3C 3J7 (Canada)
 Publication Date:
 OSTI Identifier:
 22521942
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Astrophysical Journal; Journal Volume: 813; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AXIAL SYMMETRY; COMPUTERIZED SIMULATION; CONVECTION; LAYERS; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; RAYLEIGHTAYLOR INSTABILITY; SOLAR ACTIVITY; SUN; TWODIMENSIONAL SYSTEMS
Citation Formats
Lawson, Nicolas, Strugarek, Antoine, and Charbonneau, Paul, Email: nicolas.laws@gmail.ca, Email: strugarek@astro.umontreal.ca, Email: paulchar@astro.umontreal.ca. EVIDENCE OF ACTIVE MHD INSTABILITY IN EULAGMHD SIMULATIONS OF SOLAR CONVECTION. United States: N. p., 2015.
Web. doi:10.1088/0004637X/813/2/95.
Lawson, Nicolas, Strugarek, Antoine, & Charbonneau, Paul, Email: nicolas.laws@gmail.ca, Email: strugarek@astro.umontreal.ca, Email: paulchar@astro.umontreal.ca. EVIDENCE OF ACTIVE MHD INSTABILITY IN EULAGMHD SIMULATIONS OF SOLAR CONVECTION. United States. doi:10.1088/0004637X/813/2/95.
Lawson, Nicolas, Strugarek, Antoine, and Charbonneau, Paul, Email: nicolas.laws@gmail.ca, Email: strugarek@astro.umontreal.ca, Email: paulchar@astro.umontreal.ca. Tue .
"EVIDENCE OF ACTIVE MHD INSTABILITY IN EULAGMHD SIMULATIONS OF SOLAR CONVECTION". United States.
doi:10.1088/0004637X/813/2/95.
@article{osti_22521942,
title = {EVIDENCE OF ACTIVE MHD INSTABILITY IN EULAGMHD SIMULATIONS OF SOLAR CONVECTION},
author = {Lawson, Nicolas and Strugarek, Antoine and Charbonneau, Paul, Email: nicolas.laws@gmail.ca, Email: strugarek@astro.umontreal.ca, Email: paulchar@astro.umontreal.ca},
abstractNote = {We investigate the possible development of magnetohydrodynamical instabilities in the EULAGMHD “millennium simulation” of Passos and Charbonneau. This simulation sustains a largescale magnetic cycle characterized by solarlike polarity reversals taking place on a regular multidecadal cadence, and in which zonally oriented bands of strong magnetic fields accumulate below the convective layers, in response to turbulent pumping from above in successive magnetic halfcycles. Key aspects of this simulation include low numerical dissipation and a strongly subadiabatic fluid layer underlying the convectively unstable layers corresponding to the modeled solar convection zone. These properties are conducive to the growth and development of twodimensional instabilities that are otherwise suppressed by stronger dissipation. We find evidence for the action of a nonaxisymmetric magnetoshear instability operating in the upper portions of the stably stratified fluid layers. We also investigate the possibility that the Tayler instability may be contributing to the destabilization of the largescale axisymmetric magnetic component at high latitudes. On the basis of our analyses, we propose a global dynamo scenario whereby the magnetic cycle is driven primarily by turbulent dynamo action in the convecting layers, but MHD instabilities accelerate the dissipation of the magnetic field pumped down into the overshoot and stable layers, thus perhaps significantly influencing the magnetic cycle period. Support for this scenario is found in the distinct global dynamo behaviors observed in an otherwise identical EULAGMHD simulations, using a different degree of subadiabaticity in the stable fluid layers underlying the convection zone.},
doi = {10.1088/0004637X/813/2/95},
journal = {Astrophysical Journal},
number = 2,
volume = 813,
place = {United States},
year = {Tue Nov 10 00:00:00 EST 2015},
month = {Tue Nov 10 00:00:00 EST 2015}
}

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