MHD SIMULATIONS OF CORONAL SUPRA-ARCADE DOWNFLOWS INCLUDING ANISOTROPIC THERMAL CONDUCTION
- Instituto de Investigaciones en Astronomía Teórica y Experimental (IATE), Córdoba (Argentina)
Coronal supra-arcade downflows (SADs) are observed as dark trails descending toward hot turbulent-fan-shaped regions. Due to the large temperature values and gradients in these fan regions, the thermal conduction (TC) should be very efficient. While several models have been proposed to explain the triggering and the evolution of SADs, none of these scenarios address a systematic consideration of TC. Thus, we accomplish this task numerically simulating the evolution of SADs within this framework. That is, SADs are conceived as voided (subdense) cavities formed by nonlinear waves triggered by downflowing bursty localized reconnection events in a perturbed hot fan. We generate a properly turbulent fan, obtained by a stirring force that permits control of the energy and vorticity input in the medium where SADs develop. We include anisotropic TC and consider plasma properties consistent with observations. Our aim is to study whether it is possible to prevent SADs from vanishing by thermal diffusion. We find that this will be the case, depending on the turbulence parameters, in particular if the magnetic field lines are able to envelope the voided cavities, thermally isolating them from the hot environment. Velocity shear perturbations that are able to generate instabilities of the Kelvin–Helmholtz type help to produce magnetic islands, extending the lifetime of SADs.
- OSTI ID:
- 22667161
- Journal Information:
- Astrophysical Journal, Vol. 832, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COSMOLOGY AND ASTRONOMY
ANISOTROPY
COMPUTERIZED SIMULATION
DISTURBANCES
EVOLUTION
HELMHOLTZ INSTABILITY
INSTABILITY
LIFETIME
MAGNETIC FIELDS
MAGNETIC ISLANDS
MAGNETOHYDRODYNAMICS
PERTURBATION THEORY
PLASMA
SHOCK WAVES
STIRRING
SUN
THERMAL CONDUCTION
THERMAL DIFFUSION
TURBULENCE
VELOCITY