Start year
1999
Organizational Unit
Organizing institutions
General
Description
Magnetic fields are at the base of star formation and stellar structure and evolution. When stars are born, magnetic fields brake the rotation during the collapse of the mollecular cloud. In the end of the life of a star, magnetic fields can play a key role in the form of the strong winds that lead to the last stages of stellar evolution. During the whole adult life of a star, magnetic fields are the origin of stellar activity. Our Sun has magnetic fields that give rise to such spectacular activity that impacts the climate on Earth. The magnetic activity in other stars is, in some cases, of orders of magnitude more intense than the solar one, influencing – often drastically – the transport of chemical species and angular momentum, as well as affecting the possible planetary systems around them.
The aim of this project is the study of the diverse manifestations of the magnetic field that can be observed in the solar atmosphere and in other stars. These include distinct structures as sunspots, weak quiet-sun fields or chromospheric and coronal features such as filaments and prominences. The following research topics have been gradually faced:
Solar magnetism
1. Structure and evolution of Sunspot magnetic fields.
2. Structure and evolution of quiet Sun magnetic fields.
3. Structure and evolution of the magnetism of the chromosphere and of chromospheric strcutures (promiences, spicules,...)
4. Structure and evolution or coronal loops.
5. Structure and evolution of the Sun's global field. Studies of the activity cycle.
6. Empirical study of propagation of magnetohydrodynamic waves in magnetic structures.
7. Empirical study of energy transfer mechanisms related with the heating of the external atmospheric layers.
8. Empirical study of the influence of partial ionisation in the dynamics of the solar atmosphere.
9. Participation in the European Solar Telescope project.
Stellar magnetism
1. Development of numerical tools to diagnose stellar magnetic fields, both in the surface and in the chromsphere.
2. Study of magnetic fields in stellar prominences.
3. Study of the role of magnetic fields in the late stages of stellar evolution.
Members
Principal investigator
Tobías
Felipe García
Project staff
Elena
Khomenko Shchukina
Íñigo
Arregui Uribe-Echevarría
Andrés
Asensio Ramos
Carlos Humberto
Domínguez-Tagle Paredes
María Jesús
Martínez González
Juan Carlos
Trelles Arjona
Carlos
Westendorp Plaza
Collaborators
Héctor David
Socas Navarro
Dr.
J.C. del Toro Iniesta
Dr.
R. Kostik
Dr.
N. Shchukina
Dr.
V. Olshevsky
Dr.
A. Sainz Dalda
Dr.
W. Schmidt
Dr.
Th. Berkefeld
Dr.
S.K. Solanki
Dr.
A. Gandorfer
Prof.
P. Cally
Dr.
S. Shelyag
Dr.
M. Stangalini
Dr.
C. Beck
Dr.
C. Kuckein
Dr.
C. Quintero Noda
Dr.
I. Calvo Santamaria
Dr.
C. González Fernández
Dr.
J.de la Cruz Rodríguez
Dr.
M. Leitzinger
Dr.
A. Pastor Yabar
Dr.
A. López Ariste
Dr.
Franco Leone
Dr.
R. Manso Sainz
Dr.
Luis R Bellot Rubio
Results
- Spiral waves in sunspots: They have been interpreted as magnetoacoustic waves propagating from the interior to the atmosphere following the direction of the magnetic field. We have characterized the magnetic field topology, dismissing the twist of the field lines as the cause of the spiral shape (Felipe et al. 2019).
- Magnetic response to umbral flashes: Simultaneous spectropolarimetric observations of the chromospheric He I 10830 and Ca II 8542 lines have been used to estimate the fluctuations of the magnetic field associated to shock waves. The shocks cause expansion of the magnetic field lines (Houston et al. 2018, including A. Asensio Ramos).
Scientific activity
Related publications
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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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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 -
Signatures of sunspot oscillations and the case for chromospheric resonancesSunspots host a large variety of oscillatory phenomena, whose properties depend on the nature of the wave modes and the magnetic and thermodynamic structure of the spot. Umbral chromospheric oscillations exhibit significant differences compared to their photospheric counterparts. They show an enhanced power and a shorter dominant period, from wavesFelipe, Tobías
Advertised on:
02021 -
Accurately constraining velocity information from spectral imaging observations using machine learning techniquesDetermining accurate plasma Doppler (line-of-sight) velocities from spectroscopic measurements is a challenging endeavour, especially when weak chromospheric absorption lines are often rapidly evolving and, hence, contain multiple spectral components in their constituent line profiles. Here, we present a novel method that employs machine learningMacBride, Conor D. et al.
Advertised on:
22021 -
Coronal Heating by MHD WavesThe heating of the solar chromosphere and corona to the observed high temperatures, imply the presence of ongoing heating that balances the strong radiative and thermal conduction losses expected in the solar atmosphere. It has been theorized for decades that the required heating mechanisms of the chromospheric and coronal parts of the activeVan Doorsselaere, Tom et al.
Advertised on:
122020 -
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.
Advertised on:
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.
Advertised on:
102020 -
The Polarimetric and Helioseismic Imager on Solar OrbiterAims: This paper describes the Polarimetric and Helioseismic Imager on the Solar Orbiter mission (SO/PHI), the first magnetograph and helioseismology instrument to observe the Sun from outside the Sun-Earth line. It is the key instrument meant to address the top-level science question: How does the solar dynamo work and drive connections betweenSolanki, S. K. et al.
Advertised on:
102020 -
Resonant absorption: Transformation of compressive motions into vortical motionsThis paper investigates the changes in spatial properties when magnetohydrodynamic (MHD) waves undergo resonant damping in the Alfvén continuum. The analysis is carried out for a 1D cylindrical pressure-less plasma with a straight magnetic field. The effect of the damping on the spatial wave variables is determined by using complex frequencies thatGoossens, M. et al.
Advertised on:
92020 -
Chromospheric Resonances above Sunspots and Potential Seismological ApplicationsOscillations in sunspot umbrae exhibit remarkable differences between the photosphere and chromosphere. We evaluate two competing scenarios proposed for explaining those observations: a chromospheric resonant cavity and waves traveling from the photosphere to upper atmospheric layers. We have employed numerical simulations to analyze theFelipe, Tobias et al.
Advertised on:
92020 -
A chromospheric resonance cavity in a sunspot mapped with seismologySunspots are intense collections of magnetic fields that pierce through the Sun's photosphere, with their signatures extending upwards into the outermost extremities of the solar corona 1. Cutting-edge observations and simulations are providing insights into the underlying wave generation 2, configuration 3,4 and damping 5 mechanisms found inJess, David B. et al.
Advertised on:
12020 -
Quantifying the evidence for resonant damping of coronal waves with foot-point wave power asymmetryWe use Coronal Multi-channel Polarimeter (CoMP) observations of propagating waves in the solar corona together with Bayesian analysis to assess the evidence of models with resonant damping and foot-point wave power asymmetries. We considered two nested models: a reduced and a larger model. The reduced model considers resonant damping as the soleMontes-Solís, M. et al.
Advertised on:
82020 -
Determining the dynamics and magnetic fields in He I 10830 Å during a solar filament eruptionAims: We investigate the dynamics and magnetic properties of the plasma, including the line-of-sight velocity (LOS) and optical depth, as well as the vertical and horizontal magnetic fields, belonging to an erupted solar filament. Methods: The filament eruption was observed with the GREGOR Infrared Spectrograph at the 1.5-meter GREGOR telescope onKuckein, C. et al.
Advertised on:
82020 -
Numerical determination of the cutoff frequency in solar modelsContext. In stratified atmospheres, acoustic waves can only propagate if their frequency is higher than the cutoff value. The determination of the cutoff frequency is fundamental for several topics in solar physics, such as evaluating the contribution of the acoustic waves to the chromospheric heating or the application of seismic techniquesFelipe, T. et al.
Advertised on:
82020 -
Chromospheric Magnetic Field: A Comparison of He I 10830 Å Observations with Nonlinear Force-free Field ExtrapolationThe nonlinear force-free field (NLFFF) modeling has been extensively used to infer the three-dimensional magnetic field in the solar corona. One of the assumptions in the NLFFF extrapolation is that the plasma beta is low, but this condition is considered to be incorrect in the photosphere. We examine direct measurements of the chromosphericKawabata, Yusuke et al.
Advertised on:
72020 -
On the Magnetic Nature of an Exploding Granule as Revealed by Sunrise/IMaXWe study the photospheric evolution of an exploding granule observed in the quiet Sun at high spatial (∼0"3) and temporal (31.5 s) resolution by the imaging magnetograph Sunrise/IMaX in 2009 June. These observations show that the exploding granule is cospatial to a magnetic flux emergence event occurring at mesogranular scale (up to ∼12 Mm 2 area)Guglielmino, Salvo L. et al.
Advertised on:
62020 -
Numerical simulations of large-amplitude oscillations in flux rope solar prominencesContext. Large-amplitude oscillations (LAOs) of solar prominences are a very spectacular, but poorly understood, phenomena. These motions have amplitudes larger than 10 km s -1 and can be triggered by the external perturbations such as Moreton or EIT waves. Aims: Our aim is to analyze the properties of LAOs using realistic prominence models and theLiakh, V. et al.
Advertised on:
52020
