Start year
2007
Organizational Unit
Organizing institutions
General
Description
Magnetic fields pervade all astrophysical plasmas and govern most of the variability in the Universe at intermediate time scales. They are present in stars across the whole Hertzsprung-Russell diagram, in galaxies, and even perhaps in the intergalactic medium. Polarized light provides the most reliable source of information at our disposal for the remote sensing of astrophysical magnetic fields, including those on the Sun. In particular, the diagnostics of solar and stellar magnetic fields requires the measurement and physical interpretation of polarization signatures in spectral lines, which are induced by various physical mechanisms taking place at the atomic level. In addition to the familiar Zeeman effect, polarization can also be generated by various other physical processes, such as atomic level polarization induced by anisotropic pumping mechanisms, quantum interference between fine-structured or hyperfine-structured energy levels, the Hanle effect, etc. Interestingly, the polarization produced by such mechanisms is sensitive to the physical conditions of the astrophysical plasma under consideration and, in particular, to the presence of magnetic fields in a parameter domain that goes from field intensities as small as 1 micro-G to many thousands of Gauss.
The main objective of this project is to explore in depth the physics and origin of polarized radiation in astrophysical plasmas as well as its diagnostic use for understanding cosmical magnetic fields, with emphasis on the magnetism of the extended solar atmosphere. Our investigations deal with:
-the theoretical understanding of relevant polarization physics, which requires new insights into the quantum theory of polarized light scattering in the presence of magnetic and electric fields.
-the development of plasma diagnostic tools for the investigation of astrophysical magnetic fields, with emphasis on the magnetism of the extended solar atmosphere, circumstellar envelopes and planetary nebulae.
-spectropolarimetric observations and their physical interpretation.
-radiative transfer in three-dimensional models of stellar atmospheres, resulting from magneto-hydrodynamical simulations.
-atomic and molecular spectroscopy and spectro-polarimetry, with applications in several fields of astrophysics.
This research project is formed by a group of scientists convinced of the importance of complementing theoretical and observational investigations in order to face some of the present challenges of 21st century Astrophysics.
Members
Principal investigator
Tanausú del
Pino Alemán
Project staff
Andrés
Asensio Ramos
Javier
Trujillo Bueno
Héctor David
Socas Navarro
Nikola
Vitas
Andrii
Sukhorukov
Ángel Manuel de
Vicente Garrido
Fernando
Moreno Insertis
Supriya
Hebbur Dayananda
Sara
Esteban Pozuelo
Edgar Samuel
Carlín Ramírez
Collaborators
Carlos
Allende Prieto
Íñigo
Arregui Uribe-Echevarría
Cristina
Ramos Almeida
Dr.
M. Bianda
Dr.
R. Ramelli
Dr.
L. Belluzzi
Dr.
R. Casini
Dr.
R. Centeno
Dr.
J. de la Cruz
Dr.
N. Shchukina
Dr.
H. Uitenbroek
Dr.
D. Mckenzie
Dr.
R. Ishikawa
Basilio
Ruiz Cobo
María Jesús
Martínez González
Results
- We applied deep learning techniques to the analysis of observations. Using convolutional neural networks, we developed techniques for the deconvolution of observational data. These techniques were also used to accelerate the deconvolution process of ground-based observations, achieving a cadence of around a hundred images processed per second.
- We developed an inference technique based on bayesian statistics in order to interpret the observations provided by the CLASP international experiment. By parametrizing a state-of-the-art magneto-hydrodynamical model of the solar atmosphere, we found that the geometrical complexity of the transition region must be much more complex than the one provided by the model.
- We solved the problem of polarized radiation transfer in magneto-convection simulations that account for small-scale dynamo action for the Sr I line at 460.7 nm. We found that the model with most of the convection zone magnetized close to the equipartition and a surface mean field strength of 170G is compatible with the available observations.
- We studied the magnetic sensitivity of the Ca I line at 422.7nm. The linear polarization at the core is sensitive to the Hanle effect, while the linear polarization in the wings is sensitive to the magneto-optical effects, as a consequence of the newly found effect resulting from the joint action of partial redistribution and the Zeeman effects.
- We studied the formation of the H-alpha, Mg II h-k, and Ca II H-K and 845.2nm in a model atmosphere of a flaring bipolar active region, solving the radiation transfer problem taking into account partial redistribution in full 3D geometry and out of local thermodynamical equilibrium. We succeeded in reproducing common observational features of such flaring regions.
Scientific activity
Related publications
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Rubidium abundances in solar metallicity starsContext. Rubidium is one of the few elements produced by the neutron capture s- and r-processes in almost equal proportions. Recently, a Rb deficiency ([Rb/Fe] < 0.0), amounting to a factor of about two with respect to the Sun, has been found in M dwarfs of near-solar metallicity. This stands in contrast to the close-to-solar [Sr, Zr/Fe] ratiosAbia, C. et al.
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42021 -
Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST)The National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinaryRast, Mark P. et al.
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42021 -
Emergence of Internetwork Magnetic Fields through the Solar AtmosphereInternetwork (IN) magnetic fields are highly dynamic, short-lived magnetic structures that populate the interior of supergranular cells. Since they emerge all over the Sun, these small-scale fields bring a substantial amount of flux, and therefore energy, to the solar surface. Because of this, IN fields are crucial for understanding the quiet SunGošić, M. et al.
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42021 -
Evaluating the Reliability of a Simple Method to Map the Magnetic Field Azimuth in the Solar ChromosphereThe Zeeman effect is of limited utility for probing the magnetism of the quiet solar chromosphere. The Hanle effect in some spectral lines is sensitive to such magnetism, but the interpretation of the scattering polarization signals requires taking into account that the chromospheric plasma is highly inhomogeneous and dynamic (i.e., that theJurčák, Jan et al.
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42021 -
The Impact of Limited Time Resolution on the Forward-scattering Polarization in the Solar Sr I 4607 Å LineTheoretical investigations predicted that high spatiotemporal resolution observations in the Sr I 4607 Å line must show a conspicuous scattering polarization pattern at the solar disk center, which encodes information on the unresolved magnetism of the intergranular photospheric plasma. Here we present a study of the impact of limited timedel Pino Alemán, T. et al.
Advertised on:
32021 -
Temporal evolution of small-scale internetwork magnetic fields in the solar photosphereContext. While the longitudinal field that dominates in photospheric network regions has been studied extensively, small-scale transverse fields have recently been found to be ubiquitous in the quiet internetwork photosphere and this merits further study. Furthermore, few observations have been able to capture how this field evolves. Aims: We aimCampbell, R. J. et al.
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32021 -
Long-term evolution of three light bridges developed on the same sunspotOne important feature of sunspots is the presence of light bridges. These structures are elongated and bright (as compared to the umbra) features that seem to be related to the formation and evolution of sunspots. In this work, we studied the long-term evolution and the stratification of different atmospheric parameters of three light bridgesGriñón-Marín, A. B. et al.
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32021 -
Concepts for future missions to search for technosignaturesNew and unique opportunities now exist to look for technosignatures (TS) beyond traditional SETI radio searches, motivated by tremendous advances in exoplanet science and observing capabilities in recent years. Space agencies, both public and private, may be particularly interested in learning about the community's views as to the optimal methodsSocas-Navarro, Hector et al.
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52021 -
The Effects of Three-dimensional Radiative Transfer on the Resonance Polarization of the Ca I 4227 Å LineThe sizable linear polarization signals produced by the scattering of anisotropic radiation in the core of the Ca I 4227 Å line constitute an important observable for probing the inhomogeneous and dynamic plasma of the lower solar chromosphere. Here we show the results of a three-dimensional (3D) radiative transfer complete frequency redistributionJaume Bestard, J. et al.
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32021 -
Semi-empirical Models of Spicule from Inversion of Ca II 8542 Å LineWe study a solar spicule observed off-limb using high-resolution imaging spectroscopy in the Ca II 8542 Å line obtained with the CRisp Imaging SpectroPolarimeter (CRISP) on the Swedish 1 m Solar Telescope. Using a new version of the non-LTE code NICOLE specifically developed for this problem we invert the spicule single- and double-peak lineKuridze, David et al.
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22021 -
Influence of ambipolar and Hall effects on vorticity in three-dimensional simulations of magneto-convectionThis paper presents the results of the analysis of three-dimensional simulations of solar magneto-convection that include the joint action of the ambipolar diffusion and the Hall effect. Three simulation runs are compared: one including both ambipolar diffusion and the Hall effect; one including only ambipolar diffusion and one without any of theseKhomenko, E. et al.
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22021 -
Learning to do multiframe wavefront sensing unsupervised: Applications to blind deconvolutionContext. Observations from ground-based telescopes are severely perturbed by the presence of the Earth's atmosphere. The use of adaptive optics techniques has allowed us to partly overcome this limitation. However, image-selection or post-facto image-reconstruction methods applied to bursts of short-exposure images are routinely needed to reach theAsensio Ramos, A. et al.
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22021 -
Two-fluid simulations of Rayleigh-Taylor instability in a magnetized solar prominence thread. I. Effects of prominence magnetization and mass loadingSolar prominences are formed by partially ionized plasma with inter-particle collision frequencies, which generally warrant magnetohydrodynamic treatment. In this work, we explore the dynamical impacts and observable signatures of two-fluid effects in the parameter regimes when ion-neutral collisions do not fully couple the neutral and chargedPopescu Braileanu, B. et al.
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22021 -
Planet cartography with neural learned regularizationAims: Finding potential life harboring exo-Earths with future telescopes is one of the aims of exoplanetary science. Detecting signatures of life in exoplanets will likely first be accomplished by determining the bulk composition of the planetary atmosphere via reflected or transmitted spectroscopy. However, a complete understanding of theAsensio Ramos, A. et al.
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22021 -
Downflowing umbral flashes as evidence of standing waves in sunspot umbraeContext. Umbral flashes are sudden brightenings commonly visible in the core of some chromospheric lines. Theoretical and numerical modeling suggests that they are produced by the propagation of shock waves. According to these models and early observations, umbral flashes are associated with upflows. However, recent studies have reported umbralFelipe, T. et al.
Advertised on:
12021 -
Improved near optimal angular quadratures for polarised radiative transfer in 3D MHD modelsAccurate angular quadratures are crucial for the numerical solution of three-dimensional (3D) radiative transfer problems, especially when the spectral line polarisation produced by the scattering of anisotropic radiation is included. There are two requirements for obtaining an optimal quadrature and they are difficult to satisfy simultaneouslyJaume Bestard, Jaume et al.
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12021 -
Spatially resolved measurements of the solar photospheric oxygen abundanceAims: We report the results of a novel determination of the solar oxygen abundance using spatially resolved observations and inversions. We seek to derive the photospheric solar oxygen abundance with a method that is robust against uncertainties in the model atmosphere. Methods: We use observations with spatial resolution obtained at the VacuumCubas Armas, M. et al.
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112020 -
Joint action of Hall and ambipolar effects in 3D magneto-convection simulations of the quiet Sun. I. Dissipation and generation of wavesThe partial ionization of the solar plasma causes several nonideal effects such as the ambipolar diffusion, the Hall effect, and the Biermann battery effect. Here we report on the first three-dimensional realistic simulations of solar local dynamo where all three effects were taken into account. The simulations started with a snapshot of alreadyGonzález-Morales, P. A. et al.
Advertised on:
102020 -
Ubiquitous hundred-Gauss magnetic fields in solar spiculesAims: We aim to study the magnetic field in solar spicules using high-resolution spectropolarimetric observations in the Ca II 8542 Å line obtained with the Swedish 1-m Solar Telescope. Methods: The equations that result from the application of the weak field approximation (WFA) to the radiative transfer equations were used to infer the line-ofKriginsky, M. et al.
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102020 -
New Light on an Old Problem of the Cores of Solar Resonance LinesWe reexamine a 50+ yr old problem of deep central reversals predicted for strong solar spectral lines, in contrast to the smaller reversals seen in observations. We examine data and calculations for the resonance lines of H I, Mg II, and Ca II, the self-reversed cores of which form in the upper chromosphere. Based on 3D simulations, as well as dataJudge, Philip G. et al.
Advertised on:
92020
