Magnetohydrodynamic stability of line-tied coronal arcades. II - Shearless magnetic fields

S. Migliuolo; P. J. Cargill; A. W. Hood

doi:10.1086/162111

Magnetohydrodynamic stability of line-tied coronal arcades. II - Shearless magnetic fields

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Abstract

The stability of 'shearless' arcades is investigated using normal mode equations. It is found that all such equilibria are unstable to modes with very short wavelengths in the z-direction, provided the current channel is sufficiently localized in space. These unstable modes are pressure-driven interchange modes and obey lateral force balance. The algebraic minimization of the energy integral of Zweibel (1981) does describe the most unstable modes for such equilibria and does not contradict the formal minimization of Newcomb (1960). Line-tying plays no role in the stability of these shearless arcades, apart from eliminating mode rational surfaces. The unstable modes are described by interchange instabilities, and current channels that are more sharply localized in space yield larger growth rates. The role of shear as trigger for solar flares is discussed.

Original language	English
Pages (from-to)	413-418
Journal	Astrophysical Journal
Volume	281
DOIs	https://doi.org/10.1086/162111
Publication status	Published - 1 Jun 1984

Keywords

Magnetohydrodynamic Stability
Solar Corona
Solar Magnetic Field
Boundary Value Problems
Computational Fluid Dynamics
Eigenvalues
Shear Flow
Solar Flares

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10.1086/162111

http://adsabs.harvard.edu/abs/1984ApJ...281..413M

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title = "Magnetohydrodynamic stability of line-tied coronal arcades. II - Shearless magnetic fields",

abstract = "The stability of 'shearless' arcades is investigated using normal mode equations. It is found that all such equilibria are unstable to modes with very short wavelengths in the z-direction, provided the current channel is sufficiently localized in space. These unstable modes are pressure-driven interchange modes and obey lateral force balance. The algebraic minimization of the energy integral of Zweibel (1981) does describe the most unstable modes for such equilibria and does not contradict the formal minimization of Newcomb (1960). Line-tying plays no role in the stability of these shearless arcades, apart from eliminating mode rational surfaces. The unstable modes are described by interchange instabilities, and current channels that are more sharply localized in space yield larger growth rates. The role of shear as trigger for solar flares is discussed.",

keywords = "Magnetohydrodynamic Stability, Solar Corona, Solar Magnetic Field, Boundary Value Problems, Computational Fluid Dynamics, Eigenvalues, Shear Flow, Solar Flares",

author = "S. Migliuolo and Cargill, {P. J.} and Hood, {A. W.}",

year = "1984",

month = jun,

day = "1",

doi = "10.1086/162111",

language = "English",

volume = "281",

pages = "413--418",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "American Astronomical Society",

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TY - JOUR

T1 - Magnetohydrodynamic stability of line-tied coronal arcades. II - Shearless magnetic fields

AU - Migliuolo, S.

AU - Cargill, P. J.

AU - Hood, A. W.

PY - 1984/6/1

Y1 - 1984/6/1

N2 - The stability of 'shearless' arcades is investigated using normal mode equations. It is found that all such equilibria are unstable to modes with very short wavelengths in the z-direction, provided the current channel is sufficiently localized in space. These unstable modes are pressure-driven interchange modes and obey lateral force balance. The algebraic minimization of the energy integral of Zweibel (1981) does describe the most unstable modes for such equilibria and does not contradict the formal minimization of Newcomb (1960). Line-tying plays no role in the stability of these shearless arcades, apart from eliminating mode rational surfaces. The unstable modes are described by interchange instabilities, and current channels that are more sharply localized in space yield larger growth rates. The role of shear as trigger for solar flares is discussed.

AB - The stability of 'shearless' arcades is investigated using normal mode equations. It is found that all such equilibria are unstable to modes with very short wavelengths in the z-direction, provided the current channel is sufficiently localized in space. These unstable modes are pressure-driven interchange modes and obey lateral force balance. The algebraic minimization of the energy integral of Zweibel (1981) does describe the most unstable modes for such equilibria and does not contradict the formal minimization of Newcomb (1960). Line-tying plays no role in the stability of these shearless arcades, apart from eliminating mode rational surfaces. The unstable modes are described by interchange instabilities, and current channels that are more sharply localized in space yield larger growth rates. The role of shear as trigger for solar flares is discussed.

KW - Magnetohydrodynamic Stability

KW - Solar Corona

KW - Solar Magnetic Field

KW - Boundary Value Problems

KW - Computational Fluid Dynamics

KW - Eigenvalues

KW - Shear Flow

KW - Solar Flares

U2 - 10.1086/162111

DO - 10.1086/162111

M3 - Article

SN - 0004-637X

VL - 281

SP - 413

EP - 418

JO - Astrophysical Journal

JF - Astrophysical Journal

ER -

Magnetohydrodynamic stability of line-tied coronal arcades. II - Shearless magnetic fields

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Keywords

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