Opposite polarity magnetic field and convective downflows in a simulated sunspot penumbra. (arXiv:1908.06439v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Bharti_L/0/1/0/all/0/1">Lokesh Bharti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rempel_M/0/1/0/all/0/1">Matthias Rempel</a>

Recent numerical simulations and observations of sunspots show a significant
amount of opposite polarity magnetic field within the sunspot penumbra. Most of
the opposite polarity field is associated with convective downflows. We present
an analysis of 3D MHD simulations through forward modeling of synthetic Stokes
profiles of the Fesci 6301.5 AA~ and Fesci 6302.5 AA~ lines). The synthetic
Stokes profiles are spatially and spectrally degraded considering typical
instrument properties. Line bisector shifts of the Fesci 6301.5 AA~ line are
used to determine line-of-sight velocities. Far wing magnetograms are
constructed from the Stokes V profiles of the Fesci 6302.5 AA~ line. While we
find an overall good agreement between observations and simulations, the
fraction of opposite polarity magnetic field, the downflow filling factor and
the opposite polarity-downflow association are strongly affected by spatial
smearing and presence of strong gradients in the line-of-sight magnetic field
and velocity. A significant fraction of opposite polarity magnetic field and
downflows are hidden in the observations due to typical instrumental noise.
Comparing simulations that differ by more than a factor of two in grid spacing
we find that these quantities are robust within the simulations.

Recent numerical simulations and observations of sunspots show a significant
amount of opposite polarity magnetic field within the sunspot penumbra. Most of
the opposite polarity field is associated with convective downflows. We present
an analysis of 3D MHD simulations through forward modeling of synthetic Stokes
profiles of the Fesci 6301.5 AA~ and Fesci 6302.5 AA~ lines). The synthetic
Stokes profiles are spatially and spectrally degraded considering typical
instrument properties. Line bisector shifts of the Fesci 6301.5 AA~ line are
used to determine line-of-sight velocities. Far wing magnetograms are
constructed from the Stokes V profiles of the Fesci 6302.5 AA~ line. While we
find an overall good agreement between observations and simulations, the
fraction of opposite polarity magnetic field, the downflow filling factor and
the opposite polarity-downflow association are strongly affected by spatial
smearing and presence of strong gradients in the line-of-sight magnetic field
and velocity. A significant fraction of opposite polarity magnetic field and
downflows are hidden in the observations due to typical instrumental noise.
Comparing simulations that differ by more than a factor of two in grid spacing
we find that these quantities are robust within the simulations.

http://arxiv.org/icons/sfx.gif