Solar and Stellar Magnetism

    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.

    Principal investigator
    Project staff
    1. 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).
    2. 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).

    Related publications

    • Energy in density gradient
      Inhomogeneous plasmas and fluids contain energy stored in inhomogeneity and they naturally tend to relax into lower energy states by developing instabilities or by diffusion. But the actual amount of energy in such inhomogeneities has remained unknown. In the present work, the amount of energy stored in a density gradient is calculated for several
      Vranjes, J. et al.

      Advertised on:

      1
      2015
      Citations
      0
    • Magnetic and Dynamical Photospheric Disturbances Observed During an M3.2 Solar Flare
      This Letter reports on a set of full-Stokes spectropolarimetric observations in the near-infrared He i 10830 Å spectral region covering the pre-flare, flare, and post-flare phases of an M3.2 class solar flare. The flare originated on 2013 May 17 and belonged to active region NOAA 11748. We detected strong He i 10830 Å emission in the flare. The red
      Kuckein, C. et al.

      Advertised on:

      2
      2015
      Citations
      17
    • Morphology and Dynamics of Solar Prominences from 3D MHD Simulations
      In this paper we present a numerical study of the time evolution of solar prominences embedded in sheared magnetic arcades. The prominence is represented by a density enhancement in a background-stratified atmosphere and is connected to the photosphere through the magnetic field. By solving the ideal magnetohydrodynamic equations in three
      Terradas, J. et al.

      Advertised on:

      1
      2015
      Citations
      51
    • Constraining the shaping mechanism of the Red Rectangle through the spectro-polarimetry of its central star
      We carried out high-sensitivity spectro-polarimetric observations of the central star of the Red Rectangle protoplanetary nebula with the aim of constraining the mechanism that gives its biconical shape. The stellar light of the central binary system is linearly polarised since it is scattered on the dust particles of the nebula. Surprisingly, the
      Martínez González, M. J. et al.

      Advertised on:

      2
      2015
      Citations
      13
    • Hierarchical analysis of the quiet-Sun magnetism
      Standard statistical analysis of the magnetic properties of the quiet Sun rely on simple histograms of quantities inferred from maximum-likelihood estimations. Because of the inherent degeneracies, either intrinsic or induced by the noise, this approach is not optimal and can lead to highly biased results. We carried out a meta-analysis of the
      Asensio Ramos, A. et al.

      Advertised on:

      12
      2014
      Citations
      18
    • The Formation and Disintegration of Magnetic Bright Points Observed by Sunrise/IMaX
      The evolution of the physical parameters of magnetic bright points (MBPs) located in the quiet Sun (mainly in the interwork) during their lifetime is studied. First, we concentrate on the detailed description of the magnetic field evolution of three MBPs. This reveals that individual features follow different, generally complex, and rather dynamic
      Utz, D. et al.

      Advertised on:

      12
      2014
      Citations
      24
    • Fluid description of multi-component solar partially ionized plasma
      We derive self-consistent formalism for the description of multi-component partially ionized solar plasma, by means of the coupled equations for the charged and neutral components for an arbitrary number of chemical species, and the radiation field. All approximations and assumptions are carefully considered. Generalized Ohm's law is derived for
      Khomenko, E. et al.

      Advertised on:

      9
      2014
      Citations
      88
    • Synthetic Observations of Wave Propagation in a Sunspot Umbra
      Spectropolarimetric temporal series from Fe I λ6301.5 Å and Ca II infrared triplet lines are obtained by applying the Stokes synthesis code NICOLE to a numerical simulation of wave propagation in a sunspot umbra from MANCHA code. The analysis of the phase difference between Doppler velocity and intensity core oscillations of the Fe I λ6301.5 Å line
      Felipe, T. et al.

      Advertised on:

      11
      2014
      Citations
      27
    • High speed magnetized flows in the quiet Sun
      Context. We analyzed spectropolarimetric data recorded with Hinode/SP in quiet-Sun regions located at the disk center. We found single-lobed Stokes V profiles showing highly blue- and red-shifted signals. Oftentimes both types of events appear to be related to each other. Aims: We aim to set constraints on the nature and physical causes of these
      Quintero Noda, C. et al.

      Advertised on:

      9
      2014
      Citations
      13
    • Photospheric downward plasma motions in the quiet Sun
      Context. We analyze spectropolarimetric data taken with the Hinode spacecraft in quiet solar regions at the disk center. Distorted redshifted Stokes V profiles are found that show a characteristic evolution that always follows the same sequence of phases. Aims: We aim to characterize the statistical properties of these events and recover the
      Quintero Noda, C. et al.

      Advertised on:

      6
      2014
      Citations
      12
    • The History of a Quiet-Sun Magnetic Element Revealed by IMaX/SUNRISE
      Isolated flux tubes are considered to be fundamental magnetic building blocks of the solar photosphere. Their formation is usually attributed to the concentration of magnetic field to kG strengths by the convective collapse mechanism. However, the small size of the magnetic elements in quiet-Sun areas has prevented this scenario from being studied
      Requerey, I. S. et al.

      Advertised on:

      7
      2014
      Citations
      36
    • Infrared properties of blazars: putting the GASP-WEBT sources into context
      The infrared properties of blazars can be studied from the statistical point of view with the help of sky surveys, like that provided by the Wide-field Infrared Survey Explorer and the Two Micron All Sky Survey. However, these sources are known for their strong and unpredictable variability, which can be monitored for a handful of objects only. In
      Raiteri, C. M. et al.

      Advertised on:

      7
      2014
      Citations
      26
    • Determination of the cross-field density structuring in coronal waveguides using the damping of transverse waves
      Context. Time and spatial damping of transverse magnetohydrodynamic (MHD) kink oscillations is a source of information on the cross-field variation of the plasma density in coronal waveguides. Aims: We show that a probabilistic approach to the problem of determining the density structuring from the observed damping of transverse oscillations
      Arregui, I. et al.

      Advertised on:

      5
      2014
      Citations
      19
    • Upper Limits to the Magnetic Field in Central Stars of Planetary Nebulae
      More than about 20 central stars of planetary nebulae (CSPNs) have been observed spectropolarimetrically, yet no clear, unambiguous signal of the presence of a magnetic field in these objects has been found. We perform a statistical (Bayesian) analysis of all the available spectropolarimetric observations of CSPN to constrain the magnetic fields in
      Asensio Ramos, A. et al.

      Advertised on:

      6
      2014
      Citations
      15
    • Rayleigh-Taylor instability in prominences from numerical simulations including partial ionization effects
      We study the Rayleigh-Taylor instability (RTI) at a prominence-corona transition region in a non-linear regime. Our aim is to understand how the presence of neutral atoms in the prominence plasma influences the instability growth rate, as well as the evolution of velocity, magnetic field vector, and thermodynamic parameters of turbulent drops. We
      Khomenko, E. et al.

      Advertised on:

      5
      2014
      Citations
      59
    • Rayleigh-Taylor instability in partially ionized compressible plasmas: One fluid approach
      Aims: We study the modification of the classical criterion for the linear onset and growth rate of the Rayleigh-Taylor instability (RTI) in a partially ionized (PI) plasma in the one-fluid description by considering a generalized induction equation. Methods: The governing linear equations and appropriate boundary conditions, including gravitational
      Díaz, A. J. et al.

      Advertised on:

      4
      2014
      Citations
      34
    • Observations and Implications of Large-amplitude Longitudinal Oscillations in a Solar Filament
      On 2010 August 20, an energetic disturbance triggered large-amplitude longitudinal oscillations in a nearby filament. The triggering mechanism appears to be episodic jets connecting the energetic event with the filament threads. In the present work, we analyze this periodic motion in a large fraction of the filament to characterize the underlying
      Knizhnik, K. et al.

      Advertised on:

      4
      2014
      Citations
      60
    • A search for magnetic fields on central stars in planetary nebulae
      Context. One of the possible mechanisms responsible for the panoply of shapes in planetary nebulae is the presence of magnetic fields that drive the ejection of ionized material during the proto-planetary nebula phase. Aims: Therefore, detecting magnetic fields in such objects is of key importance for understanding their dynamics. Still, magnetic
      Leone, F. et al.

      Advertised on:

      3
      2014
      Citations
      24
    • Prominence Mass Supply and the Cavity
      A prevalent but untested paradigm is often used to describe the prominence-cavity system: the cavity is under-dense because it is evacuated by supplying mass to the condensed prominence. The thermal non-equilibrium (TNE) model of prominence formation offers a theoretical framework to predict the thermodynamic evolution of the prominence and the
      Innes, D. et al.

      Advertised on:

      12
      2013
      Citations
      13
    • Properties of oscillatory motions in a facular region
      Aims: We study the properties of waves in a facular region of moderate strength in the photosphere and chromosphere. Our aim is to statistically analyse the wave periods, power, and phase relations as a function of the magnetic field strength and inclination. Methods: Our work is based on observations obtained at the German Vacuum Tower Telescope
      Kostik, R. et al.

      Advertised on:

      11
      2013
      Citations
      22

    Related talks

    No related talks were found.

    Related conferences

    No related conferences were found.