Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evershed and counter-Evershed flows in sunspot MHD simulations   There have been a few reports in the literature of counter-Evershed flows
observed in well developed sunspot penumbrae, i.e. flows directed towards the
umbra along penumbral filaments. Here we investigate the driving forces of such
counter-Evershed flows in a radiative magnetohydrodynamic simulation of a
sunspot and compare them with the forces acting on the normal Evershed flow.
The simulation covers a timespan of 100 solar hours and generates an Evershed
outflow exceeding 8 km s$^{-1}$ in the penumbra along radially aligned
filaments where the magnetic field is almost horizontal. Additionally, the
simulation produces a fast counter-Evershed flow (i.e., an inflow near $\tau =
1$) in some regions within the penumbra, reaching peak flow speeds of $\sim$12
km s$^{-1}$. The counter-Evershed flows are transient and typically last a few
hours before they turn into outflows again. By using the kinetic energy
equation and evaluating its various terms in the simulation box, we found that
the Evershed flow occurs due to overturning convection in a strongly inclined
magnetic field while the counter-Evershed flows can be well described as siphon
flows.

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The categories of this paper are: q-bio
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The categories of this paper are: bayes-an
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The categories of this paper are: chem-ph
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The categories of this paper are: econ
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The categories of this paper are: nucl-th
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
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The categories of this paper are: dg-ga
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The categories of this paper are: solv-int
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The categories of this paper are: physics
32
The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat
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The categories of this paper are: supr-con
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The categories of this paper are: ao-sci