Stratification of canopy magnetic fields in a plage region. Constraints from a spatially-regularized weak-field approximation method. (arXiv:2006.14487v2 [astro-ph.SR] UPDATED)

Stratification of canopy magnetic fields in a plage region. Constraints from a spatially-regularized weak-field approximation method. (arXiv:2006.14487v2 [astro-ph.SR] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Morosin_R/0/1/0/all/0/1">R. Morosin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rodriguez_J/0/1/0/all/0/1">J. de la Cruz Rodriguez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vissers_G/0/1/0/all/0/1">G. J. M. Vissers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yadav_R/0/1/0/all/0/1">R. Yadav</a>

The role of magnetic fields in the chromospheric heating problem remains
greatly unconstrained. Most theoretical predictions from numerical models rely
on a magnetic configuration, field strength and connectivity whose details have
not been well established with observational studies. High-resolution studies
of chromospheric magnetic fields in plage are very scarce or non-existent in
general. Our aim is to study the stratification of the magnetic field vector in
plage regions. We use high-spatial resolution full-Stokes observations acquired
with CRISP instrument at the Swedish 1-m Solar Telescope in the Mg I
$lambda$5173, Na I $lambda$5896 and Ca II $lambda$8542 lines. We have
developed a spatially-regularized weak-field approximation (WFA) method based
on the idea of spatial regularization. This method allows for a fast
computation of magnetic field maps for an extended field of view. The fidelity
of this new technique has been assessed using a snapshot from a realistic 3D
magnetohydrodynamics simulation. We have derived the depth-stratification of
the line-of-sight component of the magnetic field from the photosphere to the
chromosphere in a plage region. The magnetic fields are concentrated in the
intergranular lanes in the photosphere and expand horizontally toward the
chromosphere, filling all the space and forming a canopy. Our results suggest
that the lower boundary of this canopy must be located around 400-600 km from
the photosphere. The mean canopy total magnetic field strength in the lower
chromosphere ($zapprox760$ km) is 658 G. At $z=1160$ km we estimate
$<B_parallel>approx 417$ G. We propose a modification to the WFA that
improves its applicability to data with worse signal-to-noise ratio. These
methods provide a quick and reliable way of studying multi-layer magnetic field
observations without the many difficulties inherent to other inversion methods.

The role of magnetic fields in the chromospheric heating problem remains
greatly unconstrained. Most theoretical predictions from numerical models rely
on a magnetic configuration, field strength and connectivity whose details have
not been well established with observational studies. High-resolution studies
of chromospheric magnetic fields in plage are very scarce or non-existent in
general. Our aim is to study the stratification of the magnetic field vector in
plage regions. We use high-spatial resolution full-Stokes observations acquired
with CRISP instrument at the Swedish 1-m Solar Telescope in the Mg I
$lambda$5173, Na I $lambda$5896 and Ca II $lambda$8542 lines. We have
developed a spatially-regularized weak-field approximation (WFA) method based
on the idea of spatial regularization. This method allows for a fast
computation of magnetic field maps for an extended field of view. The fidelity
of this new technique has been assessed using a snapshot from a realistic 3D
magnetohydrodynamics simulation. We have derived the depth-stratification of
the line-of-sight component of the magnetic field from the photosphere to the
chromosphere in a plage region. The magnetic fields are concentrated in the
intergranular lanes in the photosphere and expand horizontally toward the
chromosphere, filling all the space and forming a canopy. Our results suggest
that the lower boundary of this canopy must be located around 400-600 km from
the photosphere. The mean canopy total magnetic field strength in the lower
chromosphere ($zapprox760$ km) is 658 G. At $z=1160$ km we estimate
$<B_parallel>approx 417$ G. We propose a modification to the WFA that
improves its applicability to data with worse signal-to-noise ratio. These
methods provide a quick and reliable way of studying multi-layer magnetic field
observations without the many difficulties inherent to other inversion methods.

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