Evershed and counter-Evershed flows in sunspot MHD simulations
arXiv:1712.01202 · doi:10.3847/1538-4357/aaa007
Abstract
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 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 ) in some regions within the penumbra, reaching peak flow speeds of 12 km s. 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.
Paper accepted for publication in The Astrophysical Journal
References in corpus (23)
- Radiative MHD simulation of sunspot structure
- Numerical simulations of quiet Sun magnetism: On the contribution from a small-scale dynamo
- Penumbral structure and outflows in simulated sunspots
- Numerical sunspot models: Robustness of photospheric velocity and magnetic field structure
- Magnetic Structure of Sunspots
- Fine structure, magnetic field and heating of sunspot penumbrae
- MHD simulations of penumbra fine structure
- Penumbral fine structure and driving mechanisms of large-scale flows in simulated sunspots
- Peripheral downflows in sunspot penumbrae
- Magnetostatic penumbra models with field-free gaps
- Structure of sunspot penumbral filaments: a remarkable uniformity of properties
- A dynamical model for the penumbral fine structure and the Evershed effect in sunspots
- On the fine structure of the sunspot penumbrae. II. The nature of the Evershed flow
- Emergence of magnetic flux generated in a solar convective dynamo. I: Formation of Sunspots and Active regions, and Origin of Their Asymmetries
- Convection and the origin of Evershed flows in sunspot penumbrae
- Numerical simulations of sunspot decay: On the penumbra -- Evershed flow -- moat flow connection
- Traveling Waves of Magnetoconvection and the Origin of the Evershed Effect in Sunspots
- Formation of the penumbra and start of the Evershed flow
- Sunspots: from small-scale inhomogeneities towards a global theory
- Normal and counter Evershed flows in the photospheric penumbra of a sunspot. SPINOR 2D inversions of Hinode-SOT/ SP observations
- Unusual Filaments Inside the Umbra
- Models and Observations of Sunspot Penumbrae
- Anomalous flows in a sunspot penumbra
Cited by in corpus (17)
- Detection of the strongest magnetic field in a sunspot light bridge
- 3D Radiative MHD simulations of starspots
- Superstrong photospheric magnetic fields in sunspot penumbrae
- Disambiguation of Vector Magnetograms by Stereoscopic Observations from the Solar Orbiter/Polarimetric and Helioseismic Imager (PHI) and the Solar Dynamic Observatory (SDO)/Helioseismic and Magnetic Imager (HMI)
- Properties of the Umbral Filament Observed in Active Region NOAA 12529
- Temporal Evolution of the Inverse Evershed Flow
- Penumbral decay observed in active region NOAA 12585
- Statistical analysis of the Si I 6560.58 Å line observed by CHASE
- How rare are counter Evershed flows?
- Magnetic connectivity between the light bridge and penumbra in a sunspot
- Connecting the Wilson depression to the magnetic field of sunspots
- Onset of penumbra formation
- Expulsion of counter Evershed flows from sunspot penumbrae
- Light Bridges Can Suppress the Formation of Coronal Loops
- Magnetic properties of orphan penumbrae
- Apparent Transverse Motion of Light Bridges Coupled to Coronal Loop Dynamics
- An Unusual Velocity Field in a Sunspot Penumbra