F8602 Plasma astrophysics

Faculty of Science
Spring 2025
Extent and Intensity
2/0/0. 2 credit(s) (plus extra credits for completion). Type of Completion: zk (examination).
Teacher(s)
RNDr. Miroslav Bárta, Ph.D. (lecturer), prof. Mgr. Jiří Krtička, Ph.D. (deputy)
Guaranteed by
RNDr. Miroslav Bárta, Ph.D.
Department of Theoretical Physics and Astrophysics – Physics Section – Faculty of Science
Contact Person: RNDr. Miroslav Bárta, Ph.D.
Supplier department: Department of Theoretical Physics and Astrophysics – Physics Section – Faculty of Science
Prerequisites
Basic course of plasma physics, approx. at the level of the textbook F.F. Chen: Introduction to physics of plasma
Course Enrolment Limitations
The course is offered to students of any study field.
Course objectives
The lecture loosely follows the basic courses on astrophysics, solar physics, and physics of plasmas. It aims above all at application of basic plasma-physics concepts to description and explanation of selected processes related to the magnetic activity observed in various astrophysical contexts. In illustrative examples we focus namely at the processes driving the solar and stellar eruptions and flares, together with their analogs in accretion discs. Both macro- and micro-physical (kinetic) aspects of the studied plasma processes will be addressed as well as their mutual coupling. The audience will get introduced into basic approaches for computer numerical modeling on both macro- and micro-scales in solar, space, and astrophysical plasmas. The observational aspects and mutual relations between theory/modeling and modern multi-wavelength observations (remote plasma diagnostics) shall not stay aside, too. The lecture aims at explaining general aspects of astrophysical plasmas. Nevertheless, frequently the applications will be illustrated on examples observed at the Sun, as our start represents the closest plasma-astrophysics laboratory.
Syllabus
  • Basic concepts of plasma physics and their application to processes in the solar and astrophysical plasmas. Kinetic, two-fluid and MHD description of plasmas: (single-)fluid model as an approximation and limits of its usability. Generalized Ohm’s law and anomalous (effective) electrical resistivity. Coupling of macro- and micro-scales in (almost) collision-less astro-plasmas.
  • Macroscopic structures of magnetic field with examples found in the solar atmosphere: Loops, flux ropes, and arcades. Magnetic field extrapolations: linear and non-linear force-free fields. Basics of solar magneto-hydrostatics (MHS): Example calculations of MHS equilibria – vertical slabs and flux-tubes, illustrative application to solar prominences and filaments. Magneto/hydrodynamic waves in wave-guides: Classification of the wave-modes, MHS structures as wave-guides, applications – coronal seismology.
  • Magnetic-field topology and its changes. Topological skeleton of the magnetic field: Null points, separators, separatrix surfaces and quasi-separatrix layers (QSLs). Helicity. Topological changes of the magnetic field – magnetic field-line reconnection.
  • Magnetic reconnection – deeper look: Current-layer (in)stability (tearing mode), classical reconnection models (Sweet-Parker, Petchek) and their limitations, non-linear stage of the tearing-mode instability – formation of magnetic islands/plasmoids. Plasmoid instability in highly-conductive plasmas. Dimensionality aspects: 2D vs. 3D reconnection. Magnetic configurations prone to formation of the current concentrations (current sheets): Null points, separators, (quasi)separatrix layers. (Turbulent) Energy cascades in the magnetic reconnection. Different reconnection regimes – parametric “phase diagram” of reconnection.
  • Occurrence and meaning of magnetic reconnection in the solar and astrophysical plasmas. Application of the MHD-instabilities theory and reconnection physics in solar research: Solar eruptive flares and CMEs.
  • Modeling of macroscopic processes in plasmas. Structure of the MHD equations: Energetics of the MHD processes and MHD equations in the conservative form. Approximate solution of the Riemann problem in MHD. Basic approaches to the numerical MHD modeling: Finite differences (FDM), volumes (FVM), and elements (FEM) methods of discretisation. Introduction to advanced techniques: Adaptive Mesh Refinement (AMR), parallelisation (MPI, CUDA) of numerical algorithms and high-performance computing (HPC).
  • Micro-scale kinetic processes in plasmas. Cascading energy transfer towards micro-scales and MHD turbulence. Particle acceleration, formation of non-Maxwellian distribution functions. Plasma micro-instabilities: Plasma+particle-beam systems and other non-Maxwellian configurations, generation of high-frequency plasma waves.
  • Analytical description of driven/damped waves in plasmas – quasi-linear (QL) approximation. Generalized plasma dielectric tensor. Kinetic equations for QL approximation. Energetics in the waves, absorption and emission coefficients. Stimulated emission vs. Landau damping. Feedback of plasma micro-physics to (effective) transport coefficients (e.g. resistivity) – scale coupling.
  • Numerical approaches to modeling of small-scale (kinetic) processes in the astro-plasmas: Particle codes – Test particle (TP) and Particle-in-Cell (PIC), Vlasov simulations, gyro-kinetic approximation.
  • Modern multi-wavelength observations as a remote diagnostics of solar and astrophysical plasmas and test of our models. Relations between model and observation – forward fitting and inversion methods. Significance of the diagnostic layer above numerical models – calculation of observables from the state variables of the simulated system. Numerical simulations with observation-driven boundary conditions. Example: A cascade of consecutive simulations for the space-weather predictions and the database CACTUS.
Literature
    recommended literature
  • KARLICKÝ, Marian. Plasma astrophysics. První vydání. Praha: Matfyzpress, 2014, 161 stran. ISBN 9788073782818. info
  • Kulsrud, R.M. (2005): Plasma physics for astrophysics, Princeton University Press
  • Priest, E.R. (2000): Solar magnetohydrodynamics, D. Reidel Publishing
  • Biskamp, D. (2000): Magnetic reconnection in plasmas, Cambridge University Press
  • PRESS, William H. Numerical recipes in C : the art of scientific computing. 2nd ed. Cambridge: Cambridge University Press, 1992, xxvi, 994. ISBN 0521431085. info
  • Biskamp, D. (2003): Magnetohydrodynamic turbulence, Cambridge University Press
  • Chung, T.J. (2006): Computational Fluid Dynamics, Cambridge University Press
  • Versteeg H.K., Malasekera W. : An introduction to computational fluid dynamics – The finite volume methods, Pearson/Prentice Hall 2007
  • BIRDSALL, Charles K. and A. B. LANGDON. Plasma physics via computer simulation. Bristol: Adam Hilger, 1991, 479 s. ISBN 0070053715. info
Teaching methods
Lecture supplemented by a practical exercise (in the last lesson) - implementation of a simple 1D MHD numerical code in C++ or Fortran.
Assessment methods
Oral exam. Every candidate answers two questions/topics from the lecture outline above.
Language of instruction
Czech
Further comments (probably available only in Czech)
The course is taught once in two years.
The course is taught: every other week.
General note: S.
Teacher's information
http://wave.asu.cas.cz/barta/lectures/plasma_astrophysics/
Lectures are held bi-weekly, in a block of 2x 2 hours.
The course is also listed under the following terms Spring 2021, Spring 2023.
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