The Polarization Signature of Photospheric Magnetic Fields in 3D MHD Simulations and Observations at Disk Center

Beck, C.; Fabbian, D.; Rezaei, Reza; Puschmann, K. G.

doi:10.3847/1538-4357/aa7466

Cited by 9 publications

(5 citation statements)

References 65 publications

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“…A degraded data set (rebinned and point-spread function (PSF)-convolved to approximate the Hinode resolution) yields similar values. This is within a factor 2 of the observationally based quiet-Sun values of Khomenko et al (2005) or Beck et al (2017). On the other hand, in the BPS, < B >= 48 G in the photosphere.…”

Section: Methodssupporting

confidence: 72%

Small-scale magnetic flux emergence in the quiet Sun

Moreno-Insertis,

Martinez-Sykora,

Hansteen

et al. 2018

Preprint

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Small bipolar magnetic features are observed to appear in the interior of individual granules in the quiet Sun, signaling the emergence of tiny magnetic loops from the solar interior. We study the origin of those features as part of the magnetoconvection process in the top layers of the convection zone. Two quiet-Sun magnetoconvection models, calculated with the radiation-magnetohydrodynamic (MHD) Bifrost code and with domain stretching from the top layers of the convection zone to the corona, are analyzed. Using 3D visualization as well as a posteriori spectral synthesis of Stokes parameters, we detect the repeated emergence of small magnetic elements in the interior of granules, as in the observations. Additionally, we identify the formation of organized horizontal magnetic sheets covering whole granules. Our approach is twofold, calculating statistical properties of the system, like joint probability density functions (JPDFs), and pursuing individual events via visualization tools. We conclude that the small magnetic loops surfacing within individual granules in the observations may originate from sites at or near the downflows in the granular and mesogranular levels, probably in the first 1 or 1.5 Mm below the surface. We also document the creation of granule-covering magnetic sheet-like structures through the sideways expansion of a small subphotospheric magnetic concentration picked up, and pulled out of the interior, by a nascent granule. The sheet-like structures we found in the models may match the recent observations of Centeno et al. (2017).

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Section: Methodssupporting

confidence: 72%

Small-scale magnetic flux emergence in the quiet Sun

Moreno-Insertis,

Martinez-Sykora,

Hansteen

et al. 2018

Preprint

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“…More recent work by Beck et al (2017) have quoted a value of 35 G as the average magnetic flux density of the quiet Sun region. Comparing it with the cases that we study in this paper, this would coincide with a model intermediate to Sun-v10 and Sun-v50, for which the average height of plasma-β=1 layer would correspond to around z = 900 km.…”

Section: Limitations Of the Current Study And Future Outlookmentioning

confidence: 99%

Internal Gravity Waves in the Magnetized Solar Atmosphere. II. Energy Transport

Vigeesh

Roth

Steiner

et al. 2019

ApJ

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In this second paper of the series on internal gravity waves (IGWs), we present a study of the generation and propagation of IGWs in a model solar atmosphere with diverse magnetic conditions. A magnetic field free, and three magnetic models that start with an initial, vertical, homogeneous field of 10 G, 50 G, and 100 G magnetic flux density, are simulated using the CO 5 BOLD code. We find that the IGWs are generated in similar manner in all four models in spite of the differences in the magnetic environment. The mechanical energy carried by IGWs is significantly larger than that of the acoustic waves in the lower part of the atmosphere, making them an important component of the total wave energy budget. The mechanical energy flux (10 6 -10 3 W m −2 ) is few orders of magnitude larger than the Poynting flux (10 3 -10 1 W m −2 ). The Poynting fluxes show a downward component in the frequency range corresponding to the IGWs, which confirm that these waves do not propagate upwards in the atmosphere when the fields are predominantly vertical and strong. We conclude that, in the upper photosphere, the propagation properties of IGWs depend on the average magnetic field strength and therefore these waves can be potential candidate for magnetic field diagnostics of these layers. However, their subsequent coupling to Alfvénic waves are unlikely in a magnetic environment permeated with predominantly vertical fields and therefore they may not directly or indirectly contribute to the heating of layers above plasma-β less than 1.

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“…The pair of Fe i infrared lines at 15 648 and 15 652 Å has been extensively used in the literature for polarimetric measurements since the early 1990s. Among many other works, we have the series of works entitled Infrared lines as probes of solar magnetic features that started with Muglach & Solanki (1992), or the publications of, for instance, Mathew et al (2003), Khomenko et al (2005), Bello González et al (2013), and Beck et al (2017.…”

Section: Appendix A: Fe I 15652874 åmentioning

confidence: 99%

Diagnostic capabilities of spectropolarimetric observations for understanding solar phenomena

Noda

Barklem

Gafeira

et al. 2021

A&A

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Future ground-based telescopes will expand our capabilities for simultaneous multi-line polarimetric observations in a wide range of wavelengths, from the near-ultraviolet to the near-infrared. This creates a strong demand to compare candidate spectral lines to establish a guideline of the lines that are most appropriate for each observation target. We focused in this first work on Zeeman-sensitive photospheric lines in the visible and infrared. We first examined their polarisation signals and response functions using a 1D semi-empirical atmosphere. Then we studied the spatial distribution of the line core intensity and linear and circular polarisation signals using a realistic 3D numerical simulation. We ran inversions of synthetic profiles, and we compared the heights at which we obtain a high correlation between the input and the inferred atmosphere. We also used this opportunity to revisit the atomic information we have on these lines and computed the broadening cross-sections due to collisions with neutral hydrogen atoms for all the studied spectral lines. The results reveal that four spectral lines stand out from the rest for quiet-Sun and network conditions: Fe I 5250.2, 6302, 8468, and 15 648 Å. The first three form higher in the atmosphere, and the last line is mainly sensitive to the atmospheric parameters at the bottom of the photosphere. However, as they reach different heights, we strongly recommend using at least one of the first three candidates together with the Fe I 15 648 Å line to optimise our capabilities for inferring the thermal and magnetic properties of the lower atmosphere.

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The Polarization Signature of Photospheric Magnetic Fields in 3D MHD Simulations and Observations at Disk Center

Cited by 9 publications

References 65 publications

Small-scale magnetic flux emergence in the quiet Sun

Small-scale magnetic flux emergence in the quiet Sun

Internal Gravity Waves in the Magnetized Solar Atmosphere. II. Energy Transport

Diagnostic capabilities of spectropolarimetric observations for understanding solar phenomena

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