Observational Signatures of Coronal Loop Heating and Cooling Driven by Footpoint Shuffling
Abstract
The evolution of a coronal loop is studied by means of numerical simulations of the fully compressible threedimensional magnetohydrodynamic equations using the HYPERION code. The footpoints of the loop magnetic field are advected by random motions. As a consequence, the magnetic field in the loop is energized and develops turbulent nonlinear dynamics characterized by the continuous formation and dissipation of fieldaligned current sheets: energy is deposited at small scales where heating occurs. Dissipation is nonuniformly distributed so that only a fraction of the coronal mass and volume gets heated at any time. Temperature and density are highly structured at scales that, in the solar corona, remain observationally unresolved: the plasma of our simulated loop is multithermal, where highly dynamical hotter and cooler plasma strands are scattered throughout the loop at subobservational scales. Numerical simulations of coronal loops of 50,000 km length and axial magnetic field intensities ranging from 0.01 to 0.04 T are presented. To connect these simulations to observations, we use the computed number densities and temperatures to synthesize the intensities expected in emission lines typically observed with the Extreme Ultraviolet Imaging Spectrometer on Hinode. These intensities are used to compute differential emission measure distributions using the Monte Carlo Markov Chain code, which are very similar to those derived from observations of solar active regions. We conclude that coronal heating is found to be strongly intermittent in space and time, with only small portions of the coronal loop being heated: in fact, at any given time, most of the corona is cooling down.
 Publication:

The Astrophysical Journal
 Pub Date:
 January 2016
 DOI:
 10.3847/0004637X/817/1/47
 arXiv:
 arXiv:1512.03079
 Bibcode:
 2016ApJ...817...47D
 Keywords:

 Sun: activity;
 Sun: corona;
 Sun: magnetic fields;
 turbulence;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 15 pages, 14 figures, ApJ (in press)