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26 April 2024 |
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Article overview
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Observational Signatures of Coronal Loop Heating and Cooling Driven by Footpoint Shuffling | | R. B. Dahlburg
; G. Einaudi
; B. D. Taylor
; I. Ugarte-Urra
; H. P. Warren
; A. F. Rappazzo
; M. Velli
; | | Date: |
9 Dec 2015 | | Abstract: | The evolution of a coronal loop is studied by means of numerical simulations
of the fully compressible three-dimensional 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 field-aligned current sheets: energy is deposited
at small scales where heating occurs. Dissipation is non-uniformly 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 which, in the solar
corona, remain observationally unresolved: the plasma of our simulated loop is
multi-thermal, where highly dynamical hotter and cooler plasma strands are
scattered throughout the loop at sub-observational scales. Numerical
simulations of coronal loops of 50000 km length and axial magnetic field
intensities ranging from 0.01 to 0.04 Tesla 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 (EIS) 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. | | Source: | arXiv, 1512.3079 | | Services: | Forum | Review | PDF | Favorites | |
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