SHOCKS AND THERMAL CONDUCTION FRONTS IN RETRACTING RECONNECTED FLUX TUBES

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

DOI:https://doi.org/10.1088/0004-637X/718/2/1476· OSTI ID:21455055

Guidoni, S E

We present a model for plasma heating produced by time-dependent, spatially localized reconnection within a flare current sheet separating skewed magnetic fields. The reconnection creates flux tubes of new connectivity which subsequently retract at Alfvenic speeds from the reconnection site. Heating occurs in gas-dynamic shocks (GDSs) which develop inside these tubes. Here we present generalized thin flux tube equations for the dynamics of reconnected flux tubes, including pressure-driven parallel dynamics as well as temperature-dependent, anisotropic viscosity and thermal conductivity. The evolution of tubes embedded in a uniform, skewed magnetic field, following reconnection in a patch, is studied through numerical solutions of these equations, for solar coronal conditions. Even though viscosity and thermal conductivity are negligible in the quiet solar corona, the strong GDSs generated by compressing plasma inside reconnected flux tubes generate large velocity and temperature gradients along the tube, rendering the diffusive processes dominant. They determine the thickness of the shock that evolves up to a steady state value, although this condition may not be reached in the short times involved in a flare. For realistic solar coronal parameters, this steady state shock thickness might be as long as the entire flux tube. For strong shocks at low Prandtl numbers, typical of the solar corona, the GDS consists of an isothermal sub-shock where all the compression and cooling occur, preceded by a thermal front where the temperature increases and most of the heating occurs. We estimate the length of each of these sub-regions and the speed of their propagation.

• OSTI ID: 21455055
• Journal Information: Astrophysical Journal, Vol. 718, Issue 2; Other Information: DOI: 10.1088/0004-637X/718/2/1476; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ANISOTROPY
EQUATIONS
MAGNETOHYDRODYNAMICS
NUMERICAL SOLUTION
PLASMA HEATING
SHOCK WAVES
SOLAR CORONA
SOLAR FLARES
STAR EVOLUTION
STEADY-STATE CONDITIONS
SUN
TEMPERATURE DEPENDENCE
TEMPERATURE GRADIENTS
THERMAL CONDUCTION
TIME DEPENDENCE
ATMOSPHERES
ENERGY TRANSFER
EVOLUTION
FLUID MECHANICS
HEAT TRANSFER
HEATING
HYDRODYNAMICS
MAIN SEQUENCE STARS
MATHEMATICAL SOLUTIONS
MECHANICS
SOLAR ACTIVITY
SOLAR ATMOSPHERE
STARS
STELLAR ACTIVITY
STELLAR ATMOSPHERES
STELLAR CORONAE
STELLAR FLARES