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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Non-local thermodynamic equilibrium inversions of the Si I 10827 Å spectral lineInferring the coupling of different atmospheric layers requires observing spectral lines sensitive to the atmospheric parameters, particularly the magnetic field vector, at various heights. The best way to tackle this goal is to perform multi-line observations simultaneously. For instance, the new version of the Gregor Infrared SpectrographQuintero Noda, C. et al.
Advertised on:
122024 -
CMAG: A Mission to Study and Monitor the Inner Corona Magnetic FieldMeasuring magnetic fields in the inner corona, the interface between the solar chromosphere and outer corona, is of paramount importance if we aim to understand the energetic transformations taking place there, and because it is at the origin of processes that lead to coronal heating, solar wind acceleration, and of most of the phenomena relevantOrozco Suárez, David et al.
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112023 -
Tomographic Reconstruction of the Solar K-Corona Using Neural FieldsWe explore the application of neural fields for tomographic reconstructions of the solar corona using data from the Large Angle and Spectrometric Coronagraph (LASCO)-C2 instrument. We first demonstrate their ability to recover the electron-density volume in a synthetic static case, utilizing a simulated 3D model of the corona. Our results show thatAsensio Ramos, Andrés
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112023 -
The Impact of Angle-dependent Partial Frequency Redistribution on the Scattering Polarization of the Solar Na I D LinesThe long-standing paradox of the linear polarization signal of the Na I D 1 line was recently resolved by accounting for the atom's hyperfine structure and the detailed spectral structure of the incident radiation field. That modeling relied on the simplifying angle-averaged (AA) approximation for partial frequency redistribution (PRD) inJanett, Gioele et al.
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112023 -
Polarized resonance line transfer in a spherically symmetric medium with angle-dependent partial frequency redistributionIn a stellar atmosphere, the resonance line polarization arises from scattering of limb-darkened radiation field by atoms. This spectral line polarization gets affected particularly in the wings, when the line photons suffer scattering on electrons in thermal motion. Scattering of line photons by atoms and electrons are, respectively, described bySampoorna, M. et al.
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122023 -
First Metis Detection of the Helium D<SUB>3</SUB> Line Polarization in a Large Eruptive ProminenceMetis on board Solar Orbiter is the space coronagraph developed by an Italian-German-Czech consortium. It is capable of observing solar corona and various coronal structures in the visible-light (VL) and UV (hydrogen Lyα) channels simultaneously for the first time. Here we present observations of a large eruptive prominence on 2021 April 25-26, inHeinzel, Petr et al.
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112023 -
On the Magnetic Nature of Quiet-Sun Chromospheric GrainsCa II K grains, i.e., intermittent, short-lived (about 1 minute), periodic (2-4 minutes), pointlike chromospheric brightenings, are considered to be the manifestations of acoustic waves propagating upward from the solar surface and developing into shocks in the chromosphere. After the simulations of Carlsson and Stein, we know that hot shocked gasMartínez González, María Jesús et al.
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102023 -
Magnetic Field Information in the Near-ultraviolet Fe II Lines of the CLASP2 Space ExperimentWe investigate theoretically the circular polarization signals induced by the Zeeman effect in the Fe II lines of the 279.3-280.7 nm spectral range of the CLASP2 space experiment and their suitability to infer solar magnetic fields. To this end, we use a comprehensive Fe II atomic model to solve the problem of the generation and transfer ofAfonso Delgado, David et al.
Advertised on:
92023 -
Magnetic field fluctuations in the shocked umbral chromosphereContext. Umbral chromospheric observations show the presence of magnetoacoustic shocks. Several recent studies have reported magnetic field fluctuations associated with these shock waves. The mechanism behind these periodic magnetic field changes is still an unresolved question. Aims: We aim to study the properties and origin of magnetic fieldFelipe, T. et al.
Advertised on:
82023 -
Machine learning in solar physicsThe application of machine learning in solar physics has the potential to greatly enhance our understanding of the complex processes that take place in the atmosphere of the Sun. By using techniques such as deep learning, we are now in the position to analyze large amounts of data from solar observations and identify patterns and trends that mayAsensio Ramos, Andrés et al.
Advertised on:
122023 -
Accelerating Multiframe Blind Deconvolution via Deep LearningGround-based solar-image restoration is a computationally expensive procedure that involves nonlinear optimization techniques. The presence of atmospheric turbulence produces perturbations in individual images that make it necessary to apply blind deconvolution techniques. These techniques rely on the observation of many short-exposure frames thatAsensio Ramos, Andrés et al.
Advertised on:
72023 -
iNNterpol: High-precision interpolation of stellar atmospheres with a deep neural network using a 1D convolutional auto encoder for feature extractionContext. Given the widespread availability of grids of models for stellar atmospheres, it is necessary to recover intermediate atmospheric models by means of accurate techniques that go beyond simple linear interpolation and capture the intricacies of the data. Aims: Our goal is to establish a reliable, precise, lightweight, and fast method forWestendorp Plaza, C. et al.
Advertised on:
72023 -
Opacity for realistic 3D MHD simulations of cool stellar atmospheresContext. Realistic three-dimensional time-dependent simulations of stellar near-surface convection employ the opacity binning method for the efficient and accurate computation of the radiative energy exchange. The method provides several orders of magnitude of speedup, but its implementation includes a number of free parameters. Aims: Our aim is toPerdomo García, A. et al.
Advertised on:
72023 -
The He I 10 830 Å line: Radiative transfer and differential illumination effectsWe study the formation of the Stokes profiles of the He I multiplet at 10 830 Å when relaxing two of the approximations that are typically considered in the modeling of this multiplet. Specifically, these are the lack of self-consistent radiation transfer and the assumption of equal illumination of the individual multiplet components. This He IVicente Arévalo, Andrés et al.
Advertised on:
72023 -
A study of the capabilities for inferring atmospheric information from high-spatial-resolution simulationsIn this work, we study the accuracy that can be achieved when inferring the atmospheric information from realistic numerical magneto-hydrodynamic simulations that reproduce the spatial resolution we will obtain with future observations made by the 4m class telescopes DKIST and EST. We first study multiple inversion configurations using the SIR codeQuintero Noda, C. et al.
Advertised on:
72023 -
The Magnetic Sensitivity of the (250-278 nm) Fe II Polarization SpectrumThis paper presents a theoretical investigation of the polarization and magnetic sensitivity of the near-ultraviolet (near-UV) solar spectral lines of Fe II between 250 and 278 nm. In recent years, UV spectropolarimetry has become key to uncovering the magnetism of the upper layers of the solar chromosphere. The unprecedented data obtained by theAfonso Delgado, David et al.
Advertised on:
52023 -
The Potential of the Wavelength-integrated Scattering Polarization of the Hydrogen Lyα Line for Probing the Solar ChromosphereThe intensity and the linear scattering polarization profiles of the hydrogen Lyα line encode valuable information on the thermodynamic and magnetic structure of the upper layers of the solar chromosphere. The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) sounding rocket experiment provided unprecedented spectropolarimetric data of thisAlsina Ballester, E. et al.
Advertised on:
42023 -
Estimating the longitudinal magnetic field in the chromosphere of quiet-Sun magnetic concentrationsContext. Details of the magnetic field in the quiet-Sun chromosphere are key to our understanding of essential aspects of the solar atmosphere. However, the strength and orientation of this magnetic field have not been thoroughly studied at high spatial resolution. Aims: We aim to determine the longitudinal magnetic field component (B ∥) of quietEsteban Pozuelo, S. et al.
Advertised on:
42023 -
Tomography of a Solar Plage with the Tenerife Inversion CodeWe apply the Tenerife Inversion Code (TIC) to the plage spectropolarimetric observations obtained by the Chromospheric LAyer SpectroPolarimeter (CLASP2). These unprecedented data consist of full Stokes profiles in the spectral region around the Mg II h and k lines for a single slit position, with around two thirds of the 196″ slit crossing a plageTrujillo Bueno, Javier et al.
Advertised on:
32023 -
Evidence for the Operation of the Hanle and Magneto-optical Effects in the Scattering Polarization Signals Observed by CLASP2 across the Mg II h and k LinesRadiative transfer investigations of the solar Mg II h and k resonance lines around 280 nm have shown that, while their circular polarization (Stokes V) signals arise from the Zeeman effect, the linear polarization profiles (Stokes Q and U) are dominated by the scattering of anisotropic radiation and the Hanle and magneto-optical (MO) effectsIshikawa, Ryohko et al.
Advertised on:
32023
