Numerical Simulation of Astrophysical Processes

Start year
2003
Organizational Unit

Grants related:

    General
    Description

    Numerical simulation through complex computer codes has been a fundamental tool in physics and technology research for decades. The rapid growth of computing capabilities, coupled with significant advances in numerical mathematics, has made this branch of research accessible to medium-sized research centers, bridging the gap between theoretical and experimental physics. Astrophysics is no exception to this trend. Since the late 1970s, a specialized field known as computational astrophysics has emerged, allowing us to understand a wide range of phenomena that were previously inaccessible to pure theoretical research and to account for previously unexplained observations.

    In recent decades, its primary areas of application have included (magneto)hydrodynamic phenomena and gas dynamics in various cosmic environments. For example, this includes the interiors and atmospheres of stars and planets, the interstellar medium, including magnetohydrodynamics and dynamos, accretion disks, the evolution of planetary nebulae, supernova explosions and remnants, and more. The incorporation of radiative transport equations into numerical simulations, which occurred in past decades, has added greater realism to the study of hydrodynamic processes in stellar photospheres and chromospheres.

    The current project aims to support the development of astrophysical research at the IAC based on the use of large numerical codes that require massively parallel computers and their connection with observational results. The general objective of this project is to perform calculations related to cosmic fluid dynamics and radiative transport. The topics of these calculations will focus on:

    1. Magnetized gas dynamics in the interiors and atmospheres of stars.
    2. Radiation transport and polarization signals in spectral lines based on realistic atomic and molecular models, including Hanle and Zeeman effects.
    3. Comparing theoretical/numerical results with observational data.

    This project is particularly relevant given the increasing involvement of the IAC in national and European supercomputing networks and, more generally, in large-scale supercomputer installation initiatives.

    Principal investigator

    In the following, we highlight the results of our annual year-end summary.

    Throughout the year 2022, partial ionization effects, nonequilibrium ionization effects, and multi-fluids have been one the main blocks of development both from the theoretical and numerical perspective. For instance, a generalization of the the Braginskii 1965 equations has been achieved for a general multi-species plasmas with arbitrary masses and temperatures, and where all of the viscosities and heat fluxes in the model are described by their own evolution equations. This new approach has a crucial advantage that the parallel components along the magnetic field lines do not become unbounded (infinitely large) in regimes of low-collisionallity of interest for this group as, for example, the solar corona (Hunana et al. 2022).  In this thematic block, 2D and 3D simulations, using a two-fluid model that treats the neutral and ionized species as two separate components, have also been performed to analyze the effect that the collisional interaction between both components has on the dynamics of coronal rain, the evolution of the instability of Kelvin-Helmholtz, the propagation of magneto-acoustic waves through the solar chromosphere or the heating of the plasma (Martínez-Gómez et al. 2022a). Another example of the theoretical development with potential numerical applications has been the pursuit of the effects of the ambipolar diffusion in the chromosphere from a more fundamental perspective by means of analytical solutions. The obtained solutions for cases with cylindrical symmetry are shown to constitute a demanding, but nonetheless viable, test for magnetohydrodynamic (MHD) codes that incorporate ambipolar diffusion. In addition, detailed tabulated runs of the solutions have been made available public for the community (Moreno-Insertis et al. 2022).  Lastly, nonequilibrium ionization effects of the Hydrogen atom together with the study of the Lyman α effects have been started to study in simple configurations to be applied later in realistic simulations that include the chromosphere.

     

    Improving and testing the capabilities of the available MHD codes in the solar group has been another of the major key developments carried out in 2022. For example, the results obtained by Moreno-Insertis et al. 2022 were used to check that the MHD Bifrost code is able to reproduce the theoretical solutions with sufficient accuracy up to very advanced diffusive times, as well as to explore the asymptotic properties of these theoretical solutions. In addition to that, several changes have been performed in the MANCHA code whose aim was to increase the efficiency and to add new features that will allow the researchers to perform more realistic experiments as well as exploring new research areas. For instance, MANCHA code has been extended to be able to simulate solar simulations up to the corona, adding a new module that efficiently calculates one of the key ingredients in the corona: the thermal conduction (Navarro et al. 2022). The preparation of the MANCHA code for its multi-fluid extension with radiation has also been another working branch concerning the numerical development in 2022. In addition, new equation-of-state and opacity routines have been developed that allow separating the equilibrium background contributions from those treated out of the equilibrium. Besides facing different challenges in solar physics, the huge development brought about in MANCHA is useful to study main sequence cool stars (G,K,M), which contributes to the better understanding of the stellar physics. To accomplish all these tasks, it was necessary not only to carry out numerous scaling tests and numerical experiments in local machines at the IAC, as well as on Supercomputers such as LaPalma, PICASSO, PizDaint, and MareNostrum4; but also to work together with external collaborators.

     

    During 2022, in this project there has also been a focus on different solar atmosphere phenomena and the corresponding comparison with observations. As an illustrative example, Coronal Bright Points (CBPs) have been modeled for the first time with enough realism to unravel the mechanisms that generate them and provide them with energy, being also able to explain different characteristics observed from space satellites. The comparison with observations is through synthetic SDO/AIA, Solar Orbiter EUI-HRI, and IRIS images that have been computed from the numerical experiment performed with the Bifrost code (Nóbrega-Siverio and Moreno-Insertis, 2022). Another example is the combination of 3D numerical experiments with the MoLMH code and forward modelling using Hα line to study transverse kink oscillations in prominence threads. The results contain relevant implications for the field of prominence seismology, showing that the Hα emission can be used to detect the fundamental mode of the oscillations (Martínez-Gómez et al. 2022b). In addition, ground high-resolution observations of ejective phenomena such as surges in the solar atmosphere have been analyzed, finding striking similarities with results obtained from numerical experiments. On top of that, there have also been significant contributions from the members of this project to the further advance of the observations and construction of new telescopes (Quintero et al. 2022) and satellites (De Pontieu et al. 2022, Cheung et al. 2022), using the earned knowledge from the theoretical-numerical experiments. Finally, an exploratory first attempt at understanding the physics of coronal holes and active regions from a global point of view through 2D magnetohydrostatic solutions was performed (Terradas et al. 2022), which will need of further development in the incoming years for comparisons with observations.

     

    Last but not least, state-of-the-art tools such as the ones provided by Machine Learning and Bayesian statistics have been applied to solar atmosphere problems. In this vein, a project to characterize the limits of the k-means methods and its application to solar observations was launched. In addition, new development in radiative transfer codes have being started to use in a preliminary study of machine learning approach to the computations of radiative terms. Development of the application of Bayesian techniques to the comparison of models in seismology of the solar atmosphere continued in 2022, with a review article published that accounts for the main results obtained in the last decade (Arregui 2022a). Moreover, the Bayesian formalism has been successfully applied to the prediction of the amplitude of the solar activity cycle, proposing a new methodology to quantify the goodness of both the prediction and the underlying model (Arregui 2022b).

    Related publications

    • Self-similar Approach for Rotating Magnetohydrodynamic Solar and Astrophysical Structures

      Rotating magnetic structures are common in astrophysics, from vortex tubes and tornadoes in the Sun all the way to jets in different astrophysical systems. The physics of these objects often combine inertial, magnetic, gas pressure, and gravitational terms. Also, they often show approximate symmetries that help simplify the otherwise rather

      Luna, M. et al.

      Advertised on:

      8
      2018
      Citations
      1
    • MHDSTS: a new explicit numerical scheme for simulations of partially ionised solar plasma

      The 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 of

      González-Morales, P. A. et al.

      Advertised on:

      7
      2018
      Citations
      29
    • Inversions of synthetic umbral flashes: Effects of scanning time on the inferred atmospheres

      Context. 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 and

      Felipe, T. et al.

      Advertised on:

      6
      2018
      Citations
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    • Small-scale Magnetic Flux Emergence in the Quiet Sun

      Small bipolar magnetic features are observed to appear in the interior of individual granules in the quiet Sun, signaling the emergence of tiny magnetic loops from the solar interior. We study the origin of those features as part of the magnetoconvection process in the top layers of the convection zone. Two quiet-Sun magnetoconvection models

      Moreno-Insertis, F. et al.

      Advertised on:

      6
      2018
      Citations
      26
    • GONG Catalog of Solar Filament Oscillations Near Solar Maximum

      We have cataloged 196 filament oscillations from the Global Oscillation Network Group Hα network data during several months near the maximum of solar cycle 24 (2014 January–June). Selected examples from the catalog are described in detail, along with our statistical analyses of all events. Oscillations were classified according to their velocity

      Luna, M. et al.

      Advertised on:

      6
      2018
      Citations
      35
    • On the Importance of the Nonequilibrium Ionization of Si IV and O IV and the Line of Sight in Solar Surges

      Surges are ubiquitous cool ejections in the solar atmosphere that often appear associated with transient phenomena like UV bursts or coronal jets. Recent observations from the Interface Region Imaging Spectrograph show that surges, although traditionally related to chromospheric lines, can exhibit enhanced emission in Si IV with brighter spectral

      Nóbrega-Siverio, D. et al.

      Advertised on:

      5
      2018
      Citations
      18
    • Prominence oscillations

      Prominences are intriguing, but poorly understood, magnetic structures of the solar corona. The dynamics of solar prominences has been the subject of a large number of studies, and of particular interest is the study of prominence oscillations. Ground- and space-based observations have confirmed the presence of oscillatory motions in prominences

      Arregui, I. et al.

      Advertised on:

      4
      2018
      Citations
      41
    • Rayleigh-Taylor instabilities with sheared magnetic fields in partially ionised plasmas

      Aims: 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. The

      Ruderman, M. S. et al.

      Advertised on:

      1
      2018
      Citations
      10
    • Large-amplitude Longitudinal Oscillations Triggered by the Merging of Two Solar Filaments: Observations and Magnetic Field Analysis

      We follow the eruption of two related intermediate filaments observed in Hα (from GONG) and EUV (from Solar Dynamics Observatory SDO/Atmospheric Imaging assembly AIA) and the resulting large-amplitude longitudinal oscillations of the plasma in the filament channels. The events occurred in and around the decayed active region AR12486 on 2016 January

      Luna, M. et al.

      Advertised on:

      12
      2017
      Citations
      21
    • Surges and Si IV Bursts in the Solar Atmosphere: Understanding IRIS and SST Observations through RMHD Experiments

      Surges often appear as a result of the emergence of magnetized plasma from the solar interior. Traditionally, they are observed in chromospheric lines such as Hα 6563 \mathringA and Ca II 8542 \mathringA . However, whether there is a response to the surge appearance and evolution in the Si IV lines or, in fact, in many other transition region lines

      Nóbrega-Siverio, D. et al.

      Advertised on:

      12
      2017
      Citations
      35
    • Intermittent Reconnection and Plasmoids in UV Bursts in the Low Solar Atmosphere

      Magnetic reconnection is thought to drive a wide variety of dynamic phenomena in the solar atmosphere. Yet, the detailed physical mechanisms driving reconnection are difficult to discern in the remote sensing observations that are used to study the solar atmosphere. In this Letter, we exploit the high-resolution instruments Interface Region Imaging

      Rouppe van der Voort, L. et al.

      Advertised on:

      12
      2017
      Citations
      58
    • Magnetic topological analysis of coronal bright points

      Context. We report on the first of a series of studies on coronal bright points which investigate the physical mechanism that generates these phenomena. Aims: The aim of this paper is to understand the magnetic-field structure that hosts the bright points. Methods: We use longitudinal magnetograms taken by the Solar Optical Telescope with the

      Galsgaard, K. et al.

      Advertised on:

      10
      2017
      Citations
      15
    • Comparison of Solar Fine Structure Observed Simultaneously in Lyα and Mg ii h

      The Chromospheric Lyman Alpha Spectropolarimeter (CLASP) observed the Sun in H i Lyα during a suborbital rocket flight on 2015 September 3. The Interface Region Imaging Telescope (IRIS) coordinated with the CLASP observations and recorded nearly simultaneous and co-spatial observations in the Mg ii h and k lines. The Mg ii h and Lyα lines are

      Schmit, D. et al.

      Advertised on:

      10
      2017
      Citations
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    • Dissecting the long-term emission behaviour of the BL Lac object Mrk 421

      We report on long-term multiwavelength monitoring of blazar Mrk 421 by the GLAST-AGILE Support Program of the Whole Earth Blazar Telescope (GASP-WEBT) collaboration and Steward Observatory, and by the Swift and Fermi satellites. We study the source behaviour in the period 2007-2015, characterized by several extreme flares. The ratio between the

      Carnerero, M. I. et al.

      Advertised on:

      12
      2017
      Citations
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    • Two-dimensional Radiative Magnetohydrodynamic Simulations of Partial Ionization in the Chromosphere. II. Dynamics and Energetics of the Low Solar Atmosphere

      We investigate the effects of interactions between ions and neutrals on the chromosphere and overlying corona using 2.5D radiative MHD simulations with the Bifrost code. We have extended the code capabilities implementing ion–neutral interaction effects using the generalized Ohm’s law, i.e., we include the Hall term and the ambipolar diffusion

      Martínez-Sykora, J. et al.

      Advertised on:

      9
      2017
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    • A Si I atomic model for NLTE spectropolarimetric diagnostics of the 10 827 Å line

      Aims: The Si i 10 827 Å line is commonly used for spectropolarimetric diagnostics of the solar atmosphere. First, we aim at quantifying the sensitivity of the Stokes profiles of this line to non-local thermodynamic equilibrium (NLTE) effects. Second, we aim at facilitating NLTE diagnostics of the Si i 10 827 Å line. To this end, we propose the use

      Shchukina, N. G. et al.

      Advertised on:

      7
      2017
      Citations
      17
    • Numerical simulations of quiet Sun magnetic fields seeded by the Biermann battery

      The 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 solar

      Khomenko, E. et al.

      Advertised on:

      8
      2017
      Citations
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    • Helioseismic holography of simulated sunspots: dependence of the travel time on magnetic field strength and Wilson depression

      Improving methods for determining the subsurface structure of sunspots from their seismic signature requires a better understanding of the interaction of waves with magnetic field concentrations. We aim to quantify the impact of changes in the internal structure of sunspots on local helioseismic signals. We have numerically simulated the

      Felipe, T. et al.

      Advertised on:

      8
      2017
      Citations
      8
    • High-frequency waves in the corona due to null points

      This work aims to understand the behavior of non-linear waves in the vicinity of a coronal null point. In previous works we have shown that high-frequency waves are generated in such a magnetic configuration. This paper studies those waves in detail in order to provide a plausible explanation of their generation. We demonstrate that slow magneto

      Santamaria, I. C. et al.

      Advertised on:

      6
      2017
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    • Dependence of sunspot photospheric waves on the depth of the source of solar p-modes

      Photospheric waves in sunspots moving radially outward at speeds faster than the characteristic wave velocities have been recently detected. It has been suggested that they are the visual pattern of p-modes excited around 5 Mm beneath the sunspot's surface. Using numerical simulations, we performed a parametric study of the waves observed at the

      Felipe, T. et al.

      Advertised on:

      2
      2017
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