Long-period Intensity Pulsations in Coronal Loops Explained by Thermal Non-equilibrium Cycles

In solar coronal loops, thermal non-equilibrium (TNE) is a phenomenon that can occur when the heating is both highly stratified and quasi-constant. Unambiguous observational identification of TNE would thus permit us to strongly constrain heating scenarios. While TNE is currently the standard interp...

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Bibliographic Details
Published in:The Astrophysical journal 2017-02, Vol.835 (2), p.272
Main Authors: Froment, C., Auchère, F., Aulanier, G., Miki, Z., Bocchialini, K., Buchlin, E., Solomon, J.
Format: Article
Language:English
Subjects:
Astrophysics
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
ASYMMETRY
COMPARATIVE EVALUATIONS
Coronal loops
DETECTION
EQUILIBRIUM
EVOLUTION
EXTRAPOLATION
HEATING
HYDRODYNAMICS
Observatories
Physics
PULSATIONS
Rainfall forecasting
SIMULATION
SOHO Mission
Solar activity
Solar corona
Solar observatories
STELLAR CORONAE
SUN
Sun: corona
Sun: UV radiation
Thermodynamic properties
Topology
ULTRAVIOLET RADIATION
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Summary:In solar coronal loops, thermal non-equilibrium (TNE) is a phenomenon that can occur when the heating is both highly stratified and quasi-constant. Unambiguous observational identification of TNE would thus permit us to strongly constrain heating scenarios. While TNE is currently the standard interpretation of coronal rain, the long-term periodic evolution predicted by simulations has never been observed. However, the detection of long-period intensity pulsations (periods of several hours) has been recently reported with the Solar and Heliospheric Observatory/EIT, and this phenomenon appears to be very common in loops. Moreover, the three intensity-pulsation events that we recently studied with the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA) show strong evidence for TNE in warm loops. In this paper, a realistic loop geometry from linear force-free field (LFFF) extrapolations is used as input to 1D hydrodynamic simulations. Our simulations show that, for the present loop geometry, the heating has to be asymmetrical to produce TNE. We analyze in detail one particular simulation that reproduces the average thermal behavior of one of the pulsating loop bundle observed with AIA. We compare the properties of this simulation with those deduced from the observations. The magnetic topology of the LFFF extrapolations points to the presence of sites of preferred reconnection at one footpoint, supporting the presence of asymmetric heating. In addition, we can reproduce the temporal large-scale intensity properties of the pulsating loops. This simulation further strengthens the interpretation of the observed pulsations as signatures of TNE. This consequently provides important information on the heating localization and timescale for these loops.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/835/2/272