CRITERIA FOR FLUX ROPE ERUPTION: NON-EQUILIBRIUM VERSUS TORUS INSTABILITY

Journal Article · Sun Aug 01 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/718/2/1388· OSTI ID:21455048

Demoulin, P; Aulanier, G ^[1]

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1. LESIA, Observatoire de Paris, CNRS, 5 place Jules Janssen, 92190 Meudon (France)

The coronal magnetic configuration of an active region typically evolves quietly for a few days before becoming suddenly eruptive and launching a coronal mass ejection (CME). The precise origin of the eruption is still under debate. The loss of equilibrium, or an ideal magnetohydrodynamic (MHD) instability such as torus instability are among the several mechanisms that have proposed to be responsible for the sudden eruptions. Distinct approaches have also been formulated for limited cases having circular or translation symmetry. We revisit the previous theoretical approaches setting them in the same analytical framework. The coronal field results from the contribution of a non-neutralized current channel added to a background magnetic field, which in our model is the potential field generated by two photospheric flux concentrations. The evolution on short Alfvenic timescale is governed by ideal MHD. We first show analytically that the loss of equilibrium and the stability analysis are two different views of the same physical mechanism. Second, we identify that the same physics is involved in the instabilities of circular and straight current channels. Indeed, they are just two particular limiting cases of more general current paths. A global instability of the magnetic configuration is present when the current channel is located at a coronal height, h, large enough so that the decay index of the potential field, {partial_derivative}ln |B {sub p}|/{partial_derivative}ln h, is larger than a critical value. At the limit of very thin current channels, previous analysis has found critical decay indices of 1.5 and 1 for circular and straight current channels, respectively. However, with current channels being deformable and as thick as that expected in the corona, we show that this critical index has similar values for circular and straight current channels, and is typically in the range [1.1,1.3].

• OSTI ID: 21455048
• Journal Information: Astrophysical Journal, Vol. 718, Issue 2; Other Information: DOI: 10.1088/0004-637X/718/2/1388; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
EQUILIBRIUM
ERUPTION
INSTABILITY
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
SOLAR CORONA
SOLAR FLARES
STAR EVOLUTION
SUN
ATMOSPHERES
EVOLUTION
FLUID MECHANICS
HYDRODYNAMICS
MAIN SEQUENCE STARS
MECHANICS
SOLAR ACTIVITY
SOLAR ATMOSPHERE
STARS
STELLAR ACTIVITY
STELLAR ATMOSPHERES
STELLAR CORONAE
STELLAR FLARES