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Title: 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 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 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 sub-observational 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 Carlomore » 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.« less

Authors:
;  [1];  [2];  [3];  [4];  [5];  [6]
  1. LCP and FD, Naval Research Laboratory, Washington, DC 20375 (United States)
  2. Berkeley Research Associates, Inc., Beltsville, MD 20705 (United States)
  3. College of Science, George Mason University, Fairfax, VA 22030 (United States)
  4. Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States)
  5. Advanced Heliophysics, Pasadena, CA 91106 (United States)
  6. EPSS, UCLA, Los Angeles, CA 90095 (United States)
Publication Date:
OSTI Identifier:
22521658
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 817; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPUTERIZED SIMULATION; DENSITY; EMISSION SPECTRA; EXTREME ULTRAVIOLET RADIATION; H CODES; HEATING; MAGNETIC FIELDS; MARKOV PROCESS; MASS; MONTE CARLO METHOD; PLASMA; RANDOMNESS; SOLAR CORONA; SPACE; SUN; TURBULENCE

Citation Formats

Dahlburg, R. B., Taylor, B. D., Einaudi, G., Ugarte-Urra, I., Warren, H. P., Rappazzo, A. F., and Velli, M., E-mail: rdahlbur@lcp.nrl.navy.mil. OBSERVATIONAL SIGNATURES OF CORONAL LOOP HEATING AND COOLING DRIVEN BY FOOTPOINT SHUFFLING. United States: N. p., 2016. Web. doi:10.3847/0004-637X/817/1/47.
Dahlburg, R. B., Taylor, B. D., Einaudi, G., Ugarte-Urra, I., Warren, H. P., Rappazzo, A. F., & Velli, M., E-mail: rdahlbur@lcp.nrl.navy.mil. OBSERVATIONAL SIGNATURES OF CORONAL LOOP HEATING AND COOLING DRIVEN BY FOOTPOINT SHUFFLING. United States. doi:10.3847/0004-637X/817/1/47.
Dahlburg, R. B., Taylor, B. D., Einaudi, G., Ugarte-Urra, I., Warren, H. P., Rappazzo, A. F., and Velli, M., E-mail: rdahlbur@lcp.nrl.navy.mil. Wed . "OBSERVATIONAL SIGNATURES OF CORONAL LOOP HEATING AND COOLING DRIVEN BY FOOTPOINT SHUFFLING". United States. doi:10.3847/0004-637X/817/1/47.
@article{osti_22521658,
title = {OBSERVATIONAL SIGNATURES OF CORONAL LOOP HEATING AND COOLING DRIVEN BY FOOTPOINT SHUFFLING},
author = {Dahlburg, R. B. and Taylor, B. D. and Einaudi, G. and Ugarte-Urra, I. and Warren, H. P. and Rappazzo, A. F. and Velli, M., E-mail: rdahlbur@lcp.nrl.navy.mil},
abstractNote = {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 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 sub-observational 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.},
doi = {10.3847/0004-637X/817/1/47},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 817,
place = {United States},
year = {2016},
month = {1}
}