The effects of numerical resolution, heating timescales and background heating on thermal non-equilibrium in coronal loops
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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, A&A, 597, A81; 2017b, A&A, 605, A8). 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.
Johnston , C D , Cargill , P J , Antolin , P , Hood , A W , De Moortel & Bradshaw , S J 2019 , ' The effects of numerical resolution, heating timescales and background heating on thermal non-equilibrium in coronal loops ' , Astronomy & Astrophysics , vol. 625 , A149 . https://doi.org/10.1051/0004-6361/201834742
Astronomy & Astrophysics
© 2019, ESO. This work has been made available online in accordance with the publisher's policies. This is the author created accepted version manuscript following peer review and as such may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1051/0004-6361/201834742
DescriptionFunding: European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 647214) and the UK Science and Technology Facilities Council through the consolidated grant ST/N000609/1. P.A. has received funding from his STFC Ernest Rutherford Fellowship (grant agreement No. ST/R004285/1).
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