Numerical Simulation of Astrophysical Processes

Start year
2003
Organizational Unit
    Description

    The general aim of this project is the investigation of astrophysical processes through the use of state­of­the­art numerical codes on massively parallel computers. More specifically, the research in many astrophysical fields requires an understanding of gas dynamical, magnetic, radiative transfer and gravitational phenomena not accessible to purely theoretical analysis. In the framework of this project calculation aimed at understanding the multidimensional structure and evolution of magnetic fields in stellar atmospheres and interiors are carried out, including magnetohydrodynamical aspects, radiative transfer and spectral line polarization. Special emphasis is placed on the comparison of the theoretical/numerical results with observational data.

    1. Small magnetic loops are observed to appear in the interior of individual granules in the quiet Sun. Using 3D numerical the mechanisms that produce this emergence is discovered. The results have been published in ApJ Letter 859, id. L26 and led by Prof Fernando Moreno-Insertis.
    2. In an international collaboration, almost 200 solar prominence oscillations events have been catalogued. This is the first statistically significant study of these phenomena done that also includes large-amplitude oscillations. This work has been led by Dr Manuel Luna and published in ApJ Supplement Series, 236, id. 35.

    Related publications

    • Ambipolar diffusion: Self-similar solutions and MHD code testing. Cylindrical symmetry

      Context. Ambipolar diffusion is a process occurring in partially ionised astrophysical systems that imparts a complicated mathematical and physical nature to Ohm's law. The numerical codes that solve the magnetohydrodynamic (MHD) equations have to be able to deal with the singularities that are naturally created in the system by the ambipolar

      Moreno-Insertis, F. et al.

      Advertised on:

      6
      2022
    • Solar surges related to UV bursts. Characterization through k-means, inversions, and density diagnostics

      Context. Surges are cool and dense ejections typically observed in chromospheric lines and closely related to other solar phenomena such as UV bursts or coronal jets. Even though surges have been observed for decades now, questions regarding their fundamental physical properties such as temperature and density, as well as their impact on upper

      Nóbrega-Siverio, D. et al.

      Advertised on:

      11
      2021
    • Large-amplitude longitudinal oscillations in solar prominences simulated with different resolutions

      Context. Large-amplitude longitudinal oscillations (LALOs) in solar prominences have been widely studied in recent decades. However, their damping and amplification mechanisms are not well understood. Aims: In this study, we investigate the attenuation and amplification of LALOs using high-resolution numerical simulations with progressively

      Liakh, V. et al.

      Advertised on:

      10
      2021
    • Effect of momentum and heat losses on the hydrodynamic instability of a premixed equidiffusive flame in a Hele-Shaw cell

      The linear stage of hydrodynamic instability of a laminar premixed flame propagating in a Hele-Shaw cell is investigated. Our theoretical model takes into account momentum and heat losses, temperature-dependent transport coefficients, and the continuous internal structure of the flame front. The dispersion relation is obtained numerically as a

      Han, Yifan et al.

      Advertised on:

      10
      2021
    • Evidence of the multi-thermal nature of spicular downflows. Impact on solar atmospheric heating

      Context. Spectroscopic observations of the emission lines formed in the solar transition region commonly show persistent downflows on the order of 10−15 km s−1. The cause of such downflows, however, is still not fully clear and has remained a matter of debate. Aims: We aim to understand the cause of such downflows by studying the coronal and

      Bose, Souvik et al.

      Advertised on:

      10
      2021
    • Newly formed downflow lanes in exploding granules in the solar photosphere

      Context. Exploding granules have drawn renewed interest because of their interaction with the magnetic field (either emerging or already present). Especially the newly forming downflow lanes developing in their centre seem to be eligible candidates for the intensification of magnetic fields. We analyse spectroscopic data from two different

      Ellwarth, M. et al.

      Advertised on:

      9
      2021
    • Two-fluid simulations of Rayleigh-Taylor instability in a magnetized solar prominence thread. II. Effects of collisionality

      Solar prominences are formed by partially ionized plasma with inter-particle collision frequencies generally warranting 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 charged fluids

      Popescu Braileanu, B. et al.

      Advertised on:

      6
      2021
    • Bayesian Evidence for a Nonlinear Damping Model for Coronal Loop Oscillations

      Recent observational and theoretical studies indicate that the damping of solar coronal loop oscillations depends on the oscillation amplitude. We consider two mechanisms: linear resonant absorption and a nonlinear damping model. We confront theoretical predictions from these models with observed data in the plane of observables defined by the

      Arregui, Iñigo

      Advertised on:

      7
      2021
    • Chromospheric Heating by Magnetohydrodynamic Waves and Instabilities

      The importance of the chromosphere in the mass and energy transport within the solar atmosphere is now widely recognized. This review discusses the physics of magnetohydrodynamic waves and instabilities in large-scale chromospheric structures as well as in magnetic flux tubes. We highlight a number of key observational aspects that have helped our

      Srivastava, A. K. et al.

      Advertised on:

      6
      2021
    • Simulations of the Biermann battery mechanism in two-fluid partially ionised plasmas

      Context. In the absence of an initial seed, the Biermann battery term of a non-ideal induction equation acts as a source that generates weak magnetic fields. These fields are then amplified via a dynamo mechanism. The Kelvin-Helmholtz instability is a fluid phenomenon that takes place in many astrophysical scenarios and can trigger the action of

      Martínez-Gómez, D. et al.

      Advertised on:

      6
      2021
    • A New View of the Solar Interface Region from the Interface Region Imaging Spectrograph (IRIS)

      The Interface Region Imaging Spectrograph (IRIS) has been obtaining near- and far-ultraviolet images and spectra of the solar atmosphere since July 2013. IRIS is the highest resolution observatory to provide seamless coverage of spectra and images from the photosphere into the low corona. The unique combination of near- and far-ultraviolet spectra

      De Pontieu, Bart et al.

      Advertised on:

      5
      2021
    • Large-amplitude Prominence Oscillations following Impact by a Coronal Jet

      Observational evidence shows that coronal jets can hit prominences and set them in motion. The impact leads to large-amplitude oscillations (LAOs) in the prominence. In this paper, we attempt to understand this process via 2.5D MHD numerical experiments. In our model, the jets are generated in a sheared magnetic arcade above a parasitic bipolar

      Luna, Manuel et al.

      Advertised on:

      5
      2021
    • Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST)

      The National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary

      Rast, Mark P. et al.

      Advertised on:

      4
      2021
    • Acoustic-gravity wave propagation characteristics in three-dimensional radiation hydrodynamic simulations of the solar atmosphere

      There has been tremendous progress in the degree of realism of three-dimensional radiation magneto-hydrodynamic simulations of the solar atmosphere in the past decades. Four of the most frequently used numerical codes are Bifrost, CO5BOLD, MANCHA3D and MURaM. Here we test and compare the wave propagation characteristics in model runs from these

      Fleck, B. et al.

      Advertised on:

      2
      2021
    • Influence of ambipolar and Hall effects on vorticity in three-dimensional simulations of magneto-convection

      This paper presents the results of the analysis of three-dimensional simulations of solar magneto-convection that include the joint action of the ambipolar diffusion and the Hall effect. Three simulation runs are compared: one including both ambipolar diffusion and the Hall effect; one including only ambipolar diffusion and one without any of these

      Khomenko, E. et al.

      Advertised on:

      2
      2021
    • The chromospheric component of coronal bright points. Coronal and chromospheric responses to magnetic-flux emergence

      Context. We investigate the chromospheric counterpart of small-scale coronal loops constituting a coronal bright point (CBP) and its response to a photospheric magnetic-flux increase accompanied by co-temporal CBP heating. Aims: The aim of this study is to simultaneously investigate the chromospheric and coronal layers associated with a CBP, and in

      Madjarska, Maria S. et al.

      Advertised on:

      2
      2021
    • Stability Analysis for an Interface with a Continuous Internal Structure

      A general method for solving a linear stability problem of an interface with a continuous internal structure is described. Such interfaces or fronts are commonly found in various branches of physics, such as combustion and plasma physics. It extends simplified analysis of an infinitely thin discontinuous front by means of numerical integration

      Modestov, Mikhail

      Advertised on:

      1
      2021
    • Accurately constraining velocity information from spectral imaging observations using machine learning techniques

      Determining 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 learning

      MacBride, Conor D. et al.

      Advertised on:

      2
      2021
    • Coronal Heating by MHD Waves

      The 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 active

      Van Doorsselaere, Tom et al.

      Advertised on:

      12
      2020
    • Joint action of Hall and ambipolar effects in 3D magneto-convection simulations of the quiet Sun. I. Dissipation and generation of waves

      The 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 already

      González-Morales, P. A. et al.

      Advertised on:

      10
      2020

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