How numerical treatments of the transition region modify energy flux into the solar corona
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The large temperature gradients in the solar transition region present a significant challenge to large-scale numerical modelling of the Sun’s atmosphere. In response, a variety of techniques have been developed which modify the thermodynamics of the system. This sacrifices accuracy in the transition region in favour of accurately tracking the coronal response to heating events. Invariably, the modification leads to an artificial broadening of the transition region. Meanwhile, many contemporary models of the solar atmosphere rely on tracking energy flux from the lower atmosphere, through the transition region and into the corona. In this paper, we quantify how the thermodynamic modifications affect the rate of energy injection into the corona. We consider a series of one-dimensional models of atmospheric loops with different numerical resolutions and treatments of the thermodynamics. Then, using Alfvén waves as a proxy, we consider how energy injection rates are modified in each case. We find that the thermodynamic treatment and the numerical resolution significantly modify Alfvén traveltimes, the eigenfrequencies and eigenmodes of the system, and the rate at which energy is injected into the corona. Alarmingly, we find that the modification of the energy flux is frequency dependent, meaning that it may be difficult to compare the effects of different velocity drivers on coronal heating if they are imposed below an under-resolved transition region, even if the sophisticated thermodynamic adaptations are implemented.
Howson , T A & Breu , C A 2023 , ' How numerical treatments of the transition region modify energy flux into the solar corona ' , Monthly Notices of the Royal Astronomical Society , vol. 526 , no. 1 , pp. 499–511 . https://doi.org/10.1093/mnras/stad2802
Monthly Notices of the Royal Astronomical Society
Copyright © 2023 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the final published version of the work, which was originally published at https://doi.org/10.1093/mnras/stad2802.
DescriptionFunding: The research leading to these results has received funding from the UK Science and Technology Facilities Council (consolidated grant ST/S000402/1).
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