edu.ucar.opensky::articles:21260 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-25T16:06:53.313244 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d79c712p Evershed and counter-evershed flows in sunspot MHD simulations 2018-01-08T00:00:00Z publication https://n2t.org/ark:/85065/d79c712p https://doi.org/10.3847/1538-4357/aaa007 Siu-Tapia, A. L. author Rempel, Matthias author Lagg, A. author Solanki, S. K. author UCAR/NCAR - Library publisher There have been a few reports in the literature of counter-Evershed flows observed in well-developed sunspot penumbrae, i.e., flows directed toward 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 to 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 similar to 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. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright 2018 the American Astronomical Society. None eng geoscientificInformation