The effects of numerical resolution, heating timescales and background heating on thermal non-equilibrium in coronal loops
File(s)
Accepted version
Author(s)
Type
Journal Article
Abstract
Thermal non-equilibrium (TNE) is believed to be a potentially important process in understanding some properties of
the magnetically closed solar corona. Through one-dimensional hydrodynamic models, this paper addresses the importance
of the numerical spatial resolution, footpoint heating timescales and background heating on TNE. Inadequate
transition region (TR) resolution can lead to significant discrepancies in TNE cycle behaviour, with TNE being suppressed
in under-resolved loops. A convergence on the periodicity and plasma properties associated with TNE required
spatial resolutions of less than 2 km for a loop of length 180 Mm. These numerical problems can be resolved using an
approximate method that models the TR as a discontinuity using a jump condition, as proposed by Johnston et al.
(2017a,b). The resolution requirements (and so computational cost) are greatly reduced while retaining good agreement
with fully resolved results. Using this approximate method we (i) identify different regimes for the response of coronal
loops to time-dependent footpoint heating including one where TNE does not arise and (ii) demonstrate that TNE in a
loop with footpoint heating is suppressed unless the background heating is sufficiently small. The implications for the
generality of TNE are discussed.
the magnetically closed solar corona. Through one-dimensional hydrodynamic models, this paper addresses the importance
of the numerical spatial resolution, footpoint heating timescales and background heating on TNE. Inadequate
transition region (TR) resolution can lead to significant discrepancies in TNE cycle behaviour, with TNE being suppressed
in under-resolved loops. A convergence on the periodicity and plasma properties associated with TNE required
spatial resolutions of less than 2 km for a loop of length 180 Mm. These numerical problems can be resolved using an
approximate method that models the TR as a discontinuity using a jump condition, as proposed by Johnston et al.
(2017a,b). The resolution requirements (and so computational cost) are greatly reduced while retaining good agreement
with fully resolved results. Using this approximate method we (i) identify different regimes for the response of coronal
loops to time-dependent footpoint heating including one where TNE does not arise and (ii) demonstrate that TNE in a
loop with footpoint heating is suppressed unless the background heating is sufficiently small. The implications for the
generality of TNE are discussed.
Date Issued
2019-05-29
Date Acceptance
2019-04-12
Citation
Astronomy and Astrophysics, 2019, 625
ISSN
0004-6361
Publisher
EDP Sciences
Journal / Book Title
Astronomy and Astrophysics
Volume
625
Copyright Statement
© ESO 2019
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
Sun: corona
Sun: magnetic fields
magnetohydrodynamics (MHD)
hydrodynamics
Sun: transition region
Sun: oscillations
PLASMA
CONDENSATION
INSTABILITY
SIGNATURES
DYNAMICS
WAVES
Astronomy & Astrophysics
0201 Astronomical and Space Sciences
Publication Status
Published
Article Number
ARTN A149