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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Bright Points in the Quiet Sun as Observed in the Visible and Near-UV by the Balloon-borne Observatory SUNRISEBright points (BPs) are manifestations of small magnetic elements in the solar photosphere. Their brightness contrast not only gives insight into the thermal state of the photosphere (and chromosphere) in magnetic elements, but also plays an important role in modulating the solar total and spectral irradiance. Here, we report on simultaneous highRiethmüller, T. L. et al.
Advertised on:
112010 -
Variation in sunspot properties between 1999 and 2011 as observed with the Tenerife Infrared PolarimeterAims: We study the variation in the magnetic field strength and the umbral intensity of sunspots during the declining phase of the solar cycle No. 23 and in the beginning of cycle No. 24. Methods: We analyze a sample of 183 sunspots observed from 1999 until 2011 with the Tenerife Infrared Polarimeter (TIP) at the German Vacuum Tower Telescope (VTT)Rezaei, R. et al.
Advertised on:
52012 -
Two-dimensional solar spectropolarimetry with the KIS/IAA Visible Imaging PolarimeterContext. Spectropolarimetry at high spatial and spectral resolution is a basic tool to characterize the magnetic properties of the solar atmosphere. Aims: We introduce the KIS/IAA Visible Imaging Polarimeter (VIP), a new post-focus instrument that upgrades the TESOS spectrometer at the German Vacuum Tower Telescope (VTT) into a full vectorBeck, C. et al.
Advertised on:
92010 -
The signature of chromospheric heating in Ca II H spectraContext: The heating process that balances the solar chromospheric energy losses has not yet been determined. Conflicting views exist on the source of the energy and the influence of photospheric magnetic fields on chromospheric heating. Aims: We analyze a 1-h time series of cospatial Ca II H intensity spectra and photospheric polarimetric spectraBeck, C. et al.
Advertised on:
22008 -
The magnetic flux of the quiet Sun internetwork as observed with the Tenerife infrared polarimeterContext: Observations made with the spectropolarimeter onboard the HINODE satellite have detected abundant horizontal magnetic fields in the internetwork quiet Sun. Aims: We compare the results for the horizontal fields obtained at 630 nm with ground-based observations at 1.56 μm, where the sensitivity to magnetic fields is higher than in theBeck, C. et al.
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82009 -
The energy of waves in the photosphere and lower chromosphere. II. Intensity statisticsContext. The energy source powering the solar chromosphere is still undetermined, but leaves its traces in observed intensities. Aims: We investigate the statistics of the intensity distributions as a function of the wavelength for Ca ii H and the Ca ii IR line at 854.2 nm to estimate the energy content in the observed intensity fluctuationsBeck, C. et al.
Advertised on:
82012 -
The energy of waves in the photosphere and lower chromosphere. I. Velocity statisticsContext: Acoustic waves are one of the primary suspects besides magnetic fields for the chromospheric heating process to temperatures above radiative equilibrium (RE). Aims: We derived the mechanical wave energy as seen in line-core velocities on disc centre to obtain a measure of mechanical energy flux with height for a comparison with the energyBeck, C. et al.
Advertised on:
112009 -
The Chromospheric TelescopeAims: We introduce the Chromospheric Telescope (ChroTel) at the Observatorio del Teide in Izaña on Tenerife as a new multi-wavelength imaging telescope for full-disk synoptic observations of the solar chromosphere. We describe the design of the instrument and summarize its performance during the first one and a half years of operation. We present aBethge, C. et al.
Advertised on:
102011 -
Stray-light contamination and spatial deconvolution of slit-spectrograph observationsContext. Stray light caused by scattering on optical surfaces and in the Earth's atmosphere degrades the spatial resolution of observations. Whereas post-facto reconstruction techniques are common for 2D imaging and spectroscopy, similar options for slit-spectrograph data are rarely applied. Aims: We study the contribution of stray light to the twoBeck, C. et al.
Advertised on:
112011 -
Spectroscopy at the solar limb. I. Average off-limb profiles and Doppler shifts of Ca II HAims: We present constraints on the thermodynamical structure of the chromosphere from ground-based observations of the Ca ii H line profile near and off the solar limb. Methods: We obtained a slit-spectrograph data set of the Ca ii H line with a high signal-to-noise ratio in a field of view extending 20'' across the limb. We analyzed the spectraBeck, C. et al.
Advertised on:
72011 -
Siphon flow in a cool magnetic loopContext. Siphon flows that are driven by a gas pressure difference between two photospheric footpoints of different magnetic field strength connected by magnetic field lines are a well-studied phenomenon in theory, but observational evidence is scarce. Aims. We investigate the properties of a structure in the solar chromosphere in an active regionBethge, C. et al.
Advertised on:
12012 -
Reversal-free Ca II H profiles: a challenge for solar chromosphere modeling in quiet inter-networkAims: We study chromospheric emission to understand the temperature stratification in the solar chromosphere. Methods: We observed the intensity profile of the Ca II H line in a quiet Sun region close to the disk center at the German Vacuum Tower Telescope. We analyze over 105 line profiles from inter-network regions. For comparison with theRezaei, R. et al.
Advertised on:
62008 -
Multiline Zeeman signatures through line additionContext: To obtain a significant Zeeman signature in the polarised spectra of a magnetic star, we usually “add” the contributions of numerous spectral lines; the ultimate goal is to recover the spectropolarimetric prints of the magnetic field in these line additions. Aims: Here we want to clarify the meaning of these techniques of line addition; inSemel, M. et al.
Advertised on:
92009 -
Multiline Spectropolarimetry of the Quiet Sun at 5250 and 6302 ÅThe reliability of quiet-Sun magnetic field diagnostics based on the Fe I lines at 6302 Å has been questioned by recent work. Here we present the results of a thorough study of high-resolution multiline observations taken with the new spectropolarimeter SPINOR, comprising the 5250 and 6302 Å spectral domains. The observations were analyzed usingSocas-Navarro, H. et al.
Advertised on:
22008 -
Multi-layer Study of Wave Propagation in SunspotsWe analyze the propagation of waves in sunspots from the photosphere to the chromosphere using time series of co-spatial Ca II H intensity spectra (including its line blends) and polarimetric spectra of Si I λ10,827 and the He I λ10,830 multiplet. From the Doppler shifts of these lines we retrieve the variation of the velocity along the line ofFelipe, T. et al.
Advertised on:
102010 -
Magneto-acoustic waves in sunspots from observations and numerical simulationsWe study the propagation of waves from the photosphere to the chromosphere of sunspots. From time series of cospatial Ca II H (including its line blends) intensity spectra and polarimetric spectra of Si I λ 1082.7 nm and He I λ 1083.0 nm we retrieve the line-of-sight velocity at several heights. The analysis of the phase difference andFelipe, T. et al.
Advertised on:
12011 -
Magnetic loop emergence within a granuleAims: We investigate the temporal evolution of magnetic flux emerging within a granule in the quiet-Sun internetwork at disk center. Methods: We combined IR spectropolarimetry of high angular resolution performed in two Fe i lines at 1565 nm with speckle-reconstructed G-band imaging. We determined the magnetic field parameters by a LTE inversion ofGömöry, P. et al.
Advertised on:
22010 -
Linear wavelength correlation matrices of photospheric and chromospheric spectral lines. I. Observations vs. modelingContext. The process that heats the solar chromosphere is a difficult target for observational studies because the assumption of local thermal equilibrium (LTE) is not valid in the upper solar atmosphere, which complicates the analysis of spectra. Aims: We investigate the linear correlation coefficient between the intensities at differentBeck, C. A. R. et al.
Advertised on:
22010 -
Internetwork magnetic field distribution from simultaneous 1.56 μm and 630 nm observationsAims:We study the contradictory magnetic field strength distributions retrieved from independent analyses of spectropolarimetric observations in the near-infrared (1.56 μm) and in the visible (630 nm) spectral ranges in internetwork regions. Methods: To solve this apparent controversy, we present simultaneous and co-spatial 1.56 μm and 630 nmMartínez González, M. J. et al.
Advertised on:
12008 -
Error propagation in polarimetric demodulationThe polarization analysis of light is typically carried out using modulation schemes. The light of an unknown polarization state is passed through a set of known modulation optics, and a detector is used to measure the total intensity passing the system. The modulation optics is modified several times, and, with the aid of several such measurementsAsensio Ramos, A. et al.
Advertised on:
52008
