Turbulent coronal heating mechanisms: Coupling of dynamics and thermodynamics

Abstract

Context. Photospheric motions shuffle the footpoints of the strong axial magnetic field that threads coronal loops, which gives rise to turbulent nonlinear dynamics that are characterized by the continuous formation and dissipation of field-aligned current sheets in which energy is deposited at small-scales and the heating occurs. Previous studies showed that the current sheet thickness is several orders of magnitude smaller than present-day state-of-the-art observational resolution (∼700 km). Aims. To understand coronal heating and correctly interpret observations it is crucial to study the thermodynamics of such a system in which energy is deposited at unresolved small-scales. Methods. Fully compressible three-dimensional magnetohydrodynamic simulations were carried out to understand the thermodynamics of coronal heating in the magnetically confined solar corona. Results. We show that temperature is highly structured at scales below observational resolution. It is also nonhomogeneously distributed so that only a fraction of the coronal mass and volume is heated at each time. Conclusions. This is a multi-thermal system in which hotter and cooler plasma strands are also found next to each other at sub-resolution scales and exhibit a temporal dynamics. © 2012 ESO.