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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Height variation of the cutoff frequency in a sunspot umbraContext. In the solar atmosphere, the acoustic cutoff frequency is a local quantity that depends on atmospheric height. It separates low-frequency evanescent waves from high-frequency propagating waves. Aims: We measure the cutoff frequency of slow magnetoacoustic waves at various heights of a sunspot umbra and compare the results with theFelipe, T. et al.
Advertised on:
92018 -
Temporal evolution of arch filaments as seen in He I 10 830 ÅAims: We study the evolution of an arch filament system (AFS) and of its individual arch filaments to learn about the processes occurring in them. Methods: We observed the AFS at the GREGOR solar telescope on Tenerife at high cadence with the very fast spectroscopic mode of the GREGOR Infrared Spectrograph (GRIS) in the He I 10 830 Å spectral rangeGonzález Manrique, S. J. et al.
Advertised on:
92018 -
Magnetic topology of the north solar poleThe magnetism at the poles is similar to that of the quiet Sun in the sense that no active regions are present there. However, the polar quiet Sun is somewhat different from that at the activity belt as it has a global polarity that is clearly modulated by the solar cycle. We study the polar magnetism near an activity maximum when these regionsPastor Yabar, A. et al.
Advertised on:
82018 -
MOLPOP-CEP: an exact, fast code for multi-level systemsWe present MOLPOP-CEP, a universal line transfer code that allows the exact calculation of multi-level line emission from a slab with variable physical conditions for any arbitrary atom or molecule for which atomic data exist. The code includes error control to achieve any desired level of accuracy, providing full confidence in its resultsAsensio Ramos, A. et al.
Advertised on:
92018 -
MHDSTS: a new explicit numerical scheme for simulations of partially ionised solar plasmaThe interaction of plasma with magnetic field in the partially ionised solar atmosphere is frequently modelled via a single-fluid approximation, which is valid for the case of a strongly coupled collisional media, such as solar photosphere and low chromosphere. Under the single-fluid formalism the main non-ideal effects are described by a series ofGonzález-Morales, P. A. et al.
Advertised on:
72018 -
Enhancing SDO/HMI images using deep learningContext. The Helioseismic and Magnetic Imager (HMI) provides continuum images and magnetograms with a cadence better than one per minute. It has been continuously observing the Sun 24 h a day for the past 7 yr. The trade-off between full disk observations and spatial resolution means that HMI is not adequate for analyzing the smallest-scale eventsDíaz Baso, C. J. et al.
Advertised on:
62018 -
Inversions of synthetic umbral flashes: Effects of scanning time on the inferred atmospheresContext. The use of instruments that record narrowband images at selected wavelengths is a common approach in solar observations. They allow scanning of a spectral line by sampling the Stokes profiles with two-dimensional images at each line position, but require a compromise between spectral resolution and temporal cadence. The interpretation andFelipe, T. et al.
Advertised on:
62018 -
High-resolution imaging and near-infrared spectroscopy of penumbral decayAims: Combining high-resolution spectropolarimetric and imaging data is key to understanding the decay process of sunspots as it allows us to scrutinize the velocity and magnetic fields of sunspots and their surroundings. Methods: Active region NOAA 12597 was observed on 2016 September 24 with the 1.5-meter GREGOR solar telescope using high-spatialVerma, M. et al.
Advertised on:
62018 -
The Magnetic Response of the Solar Atmosphere to Umbral FlashesChromospheric observations of sunspot umbrae offer an exceptional view of magnetoacoustic shock phenomena and the impact they have on the surrounding magnetically dominated plasma. We employ simultaneous slit-based spectro-polarimetry and spectral imaging observations of the chromospheric He I 10830 Å and Ca II 8542 Å lines to examine fluctuationsHouston, S. J. et al.
Advertised on:
62018 -
Fast-to-Alfvén Mode Conversion in the Presence of Ambipolar DiffusionIt is known that fast magnetohydrodynamic waves partially convert to upward and/or downward propagating Alfvén waves in a stratified atmosphere where Alfvén speed increases with height. This happens around the fast wave reflection height, where the fast wave’s horizontal phase speed equals the Alfvén speed (in a low-β plasma). Typically, this takesCally, P. S. et al.
Advertised on:
32018 -
Partially Ionized Plasmas in AstrophysicsPartially ionized plasmas are found across the Universe in many different astrophysical environments. They constitute an essential ingredient of the solar atmosphere, molecular clouds, planetary ionospheres and protoplanetary disks, among other environments, and display a richness of physical effects which are not present in fully ionized plasmasBallester, J. L. et al.
Advertised on:
32018 -
Solar polarimetry in the K I D2 line : A novel possibility for a stratospheric balloonOf the two solar lines, K I D1 and D2, almost all attention so far has been devoted to the D1 line, as D2 is severely affected by an O2 atmospheric band. This, however, makes the latter appealing for balloon and space observations from above (most of) the Earth's atmosphere. We estimate the residual effect of the O2 band on the K I D2 line atQuintero Noda, C. et al.
Advertised on:
32018 -
Persistent magnetic vortex flow at a supergranular vertexContext. Photospheric vortex flows are thought to play a key role in the evolution of magnetic fields. Recent studies show that these swirling motions are ubiquitous in the solar surface convection and occur in a wide range of temporal and spatial scales. Their interplay with magnetic fields is poorly characterized, however. Aims: We study theRequerey, I. S. et al.
Advertised on:
32018 -
The First Post-Kepler Brightness Dips of KIC 8462852We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started in 2015 October, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from EarthBoyajian, T. S. et al.
Advertised on:
12018 -
Bayesian coronal seismologyIn contrast to the situation in a laboratory, the study of the solar atmosphere has to be pursued without direct access to the physical conditions of interest. Information is therefore incomplete and uncertain and inference methods need to be employed to diagnose the physical conditions and processes. One of such methods, solar atmosphericArregui, I.
Advertised on:
12018 -
Rayleigh-Taylor instabilities with sheared magnetic fields in partially ionised plasmasAims: In the present study we investigate the nature of the magnetic Rayleigh-Taylor instability appearing at a tangential discontinuity in a partially ionised plasma when the effect of magnetic shear is taken into account. Methods: The partially ionised character of the plasma is described by the ambipolar diffusion in the induction equation. TheRuderman, M. S. et al.
Advertised on:
12018 -
Signatures of the impact of flare-ejected plasma on the photosphere of a sunspot light bridgeAims: We investigate the properties of a sunspot light bridge, focusing on the changes produced by the impact of a plasma blob ejected from a C-class flare. Methods: We observed a sunspot in active region NOAA 12544 using spectropolarimetric raster maps of the four Fe I lines around 15 655 Å with the GREGOR Infrared Spectrograph, narrow-bandFelipe, T. et al.
Advertised on:
122017 -
Detection of emission in the Si I 1082.7 nm line core in sunspot umbraeContext. Determining empirical atmospheric models for the solar chromosphere is difficult since it requires the observation and analysis of spectral lines that are affected by non-local thermodynamic equilibrium (NLTE) effects. This task is especially difficult in sunspot umbrae because of lower continuum intensity values in these regions withOrozco Suárez, D. et al.
Advertised on:
112017 -
DeepVel: Deep learning for the estimation of horizontal velocities at the solar surfaceMany phenomena taking place in the solar photosphere are controlled by plasma motions. Although the line-of-sight component of the velocity can be estimated using the Doppler effect, we do not have direct spectroscopic access to the components that are perpendicular to the line of sight. These components are typically estimated using methods basedAsensio Ramos, A. et al.
Advertised on:
72017 -
Numerical simulations of quiet Sun magnetic fields seeded by the Biermann batteryThe magnetic fields of the quiet Sun cover at any time more than 90% of its surface and their magnetic energy budget is crucial to explain the thermal structure of the solar atmosphere. One of the possible origins of these fields is the action of the local dynamo in the upper convection zone of the Sun. Existing simulations of the local solarKhomenko, E. et al.
Advertised on:
82017
