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Hans Goedbloed

Hans Goedbloed

Prof. Dr. J.P. Goedbloed

Advisor, DIFFER, TU/e Science Park, De Zaale 20, 5612AJ Eindhoven, the Netherlands

Professor emeritus Theoretical Plasma Physics, Physics and Astronomy Department, Utrecht University 

E-mail: goedbloed [28] differ [368] nl (goedbloed[at]differ[dot]nl)

Tel: +31 (0) 40 333 4999

ORCID: https://orcid.org/0000-0002-8794-472X

Hans Goedbloed by Henk van der Vorst

(charcoal by Henk van der Vorst)

New

Parametric Survey of Nonaxisymmetric Accretion Disk Instabilities: Magnetorotational Instability to Super-Alfvénic Rotational Instability

Authors: Nicolas Brughmans, Rony Keppens and Hans Goedbloed (Astrophysical Journal, 968:19, (20 pp), 2024)

https://doi.org/10.1017/S0022377823001058

Accretion disks are highly unstable to magnetic instabilities driven by shear flow, where classically, the axisymmetric, weak-field magnetorotational instability (MRI) has received much attention through local WKB approximations. In contrast, discrete nonaxisymmetric counterparts require a more involved analysis through a full global approach to deal with the influence of the nearby magnetohydrodynamic (MHD) continua. Recently, rigorous MHD spectroscopy identified a new type of ultralocalized, nonaxisymmetric instability in global disks with super-Alfvénic flow. These super-Alfvénic rotational instabilities (SARIs) fill vast unstable regions in the complex eigenfrequency plane with (near eigen)modes that corotate at the local Doppler velocity and are radially localized between Alfvénic resonances. Unlike discrete modes, they are utterly insensitive to the radial disk boundaries. In this work, we independently confirm the existence of these unprecedented modes using our novel spectral MHD code Legolas, reproducing and extending our earlier study with detailed eigenspectra and eigenfunctions. We calculate the growth rates of SARIs and MRI in a variety of disk equilibria, highlighting the impact of field strength and orientation, and find correspondence with analytical predictions for thin, weakly magnetized disks. We show that nonaxisymmetric modes can significantly extend instability regimes at high mode numbers, with maximal growth rates comparable to those of the MRI. Furthermore, we explicitly show a region filled with quasi-modes whose eigenfunctions are extremely localized in all directions. These modes must be ubiquitous in accretion disks, and play a role in local shearing box simulations. Finally, we revisit recent dispersion relations in the appendix, highlighting their relation to our global framework.

On boundary conditions in flux tubes with a pressure jump

Authors: Hans Goedbloed and Stefaan Poedts (Research Notes of the AAS, 8, 60, 2024)

https://doi.org/10.3847/2515-5172/ad2de1

It is proved that the recent paper by Yelagandula2023 (Ap.J. 954:178, 2023) on 'a new insight' on the boundary conditions to be applied to magnetohydrodynamic waves in magnetic flux tubes with a finite thermal pressure jump at the boundary is fundamentally wrong. It exploits the wrong variables and assumes a fixed instead of a moving boundary.

Leaky Modes in Coronal Magnetic Flux Tubes revisited

Authors: Hans Goedbloed, Rony Keppens and Stefaan Poedts (Journal of Plasma Physics, 89, 805890520, (25 pp), 2023)

https://doi.org/10.1017/S0022377823001058

It is shown that the extensive literature on leaky modes in coronal magnetic flux tubes should be revised since those modes have no physical meaning. 

The Super-Alfvénic Rotational Instability in accretion disks about black holes

Authors: Hans Goedbloed and Rony Keppens (Astrophysical Journal Supplement Series, 259:65 (41 pp), 2022 April)

Black holes are surrounded by disks consisting of hot magnetized plasma. Those disks would forever rotate at Keplerian velocity if not some anomalously large dissipation mechanism would brake the rotation and cause the plasma to fall into the black hole. For thirty years now that mechanism was ascribed to the Magneto-Rotational Instability (MRI) which would produce vertical and horizontal perturbations of the disk, but conserve the rotational symmetry (m = 0). Breaking that symmetry required breaking away from standard solution techniques by delving deeply into singular analysis. That search was facilitated by the two-year pandemic seclusion into the study resulting in the discovery of a large class of non-axisymmetric solutions that have all requisite properties for turbulent excitation of accretion. They originate from the interaction of the co- and the counter-rotating Alfvén continuous spectra producing quasi-discrete instabilities at the Doppler frequency. They are spatially highly localized in all three directions and their frequencies densely cover large twodimensional stretches of the complex frequency plane. Most important, they require a tiny amount of external energy (of the order of the machine accuracy used in the calculations) to excite them. We have termed them Super-Alfvénic Rotational Instabilities (SARIs) and conjecture that these SARIs, rather than the MRIs, excite the turbulence needed for accretion of magnetized plasma onto a black hole.

arXiv:2201.1151 [astro-ph.HE] (preprint)    
ApJS 259:65 (published version)

Latest text book

Magnetohydrodynamics of Laboratory and Astrophysical Plasmas

Authors: Hans Goedbloed, Rony Keppens, and Stefaan Poedts (Cambridge University Press, 2019)

Rony Keppens (home page)    
Stefaan Poedts (home page)

With 90% of visible matter in the Universe existing in the plasma state, an understanding of magnetohydrodynamics is essential for anyone looking to understand solar and astrophysical processes, from stars to accretion discs and galaxies; as well as laboratory applications focused on harnessing controlled fusion energy. This introduction to magnetohydrodynamics brings together the theory of plasma behaviour with advanced topics including the applications of plasma physics to thermonuclear fusion and plasmaastrophysics. Topics covered include streaming and toroidal plasmas, nonlinear dynamics, modern computational techniques, incompressible plasma turbulence and extreme transonic and relativistic plasma flows. The numerical techniques needed to apply magnetohydrodynamics are explained, allowing the reader to move from theory to application and exploit the latest algorithmic advances. Bringing together two previous volumes: Principles of Magnetohydrodynamics and Advanced Magnetohydrodynamics, and completely updated with new examples, insights and applications, this volume constitutes a comprehensive reference for students and researchers interested in plasma physics, astrophysics and thermonuclear fusion.

CONTENTS Part I. Plasma Physics Preliminaries: 1. Introduction; 2. Elements of plasma physics; 3. 'Derivation' of the macroscopic equations; Part II. Basic Magnetohydrodynamics: 4. The MHD model; 5. Waves and characteristics; 6. Spectral theory; Part III. Standard Model Applications: 7. Waves and instabilities on inhomogeneous plasmas; 8. Magnetic structures and dynamics of the solar system; 9. Cylindrical plasmas; 10. Initial value problem and wave damping; 11. Resonant absorption and wave heating; Part IV. Flow and Dissipation: 12. Waves and instabilities of stationary plasmas; 13. Shear flow and rotation; 14. Resistive plasma dynamics; 15. Computational linear MHD; Part V. Toroidal Geometry: 16. Static equilibrium of toroidal plasmas; 17. Linear dynamics of static toroidal plasmas; 18. Linear dynamics of toroidal plasmas with flow; Part VI. Nonlinear Dynamics: 19. Turbulence in incompressible magneto-fluids; 20. Computational nonlinear MHD; 21. Transonic MHD flows and shocks; 22. Ideal MHD in special relativity; Appendices.

ISBN 9781107123922 (hardback)    
https://doi.org/10.1017/9781316403679 (electronic version)

  • A workshop on "Magnetohydrodynamics: Physics for the 21 Century" was held 11-15 October 2021 at Leiden University: Workshop-Lorentz Center
  • Errata on Magnetohydrodynamics of Laboratory and Astrophysical Plasmas:      
    ErrataMagnetohydrodynamics.pdf (updated 3 November 2023)

Previous textbooks

Advanced Magnetohydrodynamics With Applications to Laboratory and Astrophysical Plasmas

Authors: Hans Goedbloed, Rony Keppens, and Stefaan Poedts (Cambridge University Press, 2010)

Rony Keppens (home page)    
Stefaan Poedts (home page)

Following on from the companion volume Principles of Magnetohydrodynamics, this textbook analyzes the applications of plasma physics to thermonuclear fusion and plasma astrophysics from the single viewpoint of MHD. This approach turns out to be ever more powerful when applied to streaming plasmas (the vast majority of visible matter in the Universe), toroidal plasmas (the most promising approach to fusion energy), and nonlinear dynamics (where it all comes together with modern computational techniques and extreme transonic and relativistic plasma flows). The textbook interweaves theory and explicit calculations of waves and instabilities of streaming plasmas in complex magnetic geometries. It is ideally suited to advanced undergraduate and graduate courses in plasma physics and astrophysics.

CONTENTS Part III. Flow and Dissipation: 12. Waves and instabilities of stationary plasmas; 13. Shear flow and rotation; 14. Resistive plasma dynamics; 15. Computational linear MHD; Part IV. Toroidal Plasmas: 16. Static equilibrium of toroidal plasmas; 17. Linear dynamics of static toroidal plasmas; 18. Linear dynamics of stationary toroidal plasmas; Part V. Nonlinear Dynamics: 19. Computational nonlinear MHD; 20. Transonic MHD flows and shocks; 21. Ideal MHD in special relativity; Appendices.

ISBN 9780521879576 (hardback)   
ISBN 9780521705240 (paperback)

  • A book presentation was held at Rijnhuizen on 11 June 2010, with musical accompaniment on the viola da gamba:   
    Bookpresentation   
    Ralph Rousseau (home page)
  • A workshop on "Advanced Magnetohydrodynamics" was held 11-15 April 2011 at Leiden University: Workshop-Lorentz Center
  • Errata on Advanced Magnetohydrodynamics   
    ErrataAdvMHD.pdf (updated 17 May 2017)

Principles of Magnetohydrodynamics With Applications to Laboratory and Astrophysical Plasmas

Authors: Hans Goedbloed and Stefaan Poedts (Cambridge University Press, 2004)

This textbook provides a modern and accessible introduction to magnetohydrodynamics (MHD). It describes the two main applications of plasma physics -- laboratory research on thermo-nuclear fusion energy and plasma-astrophysics of the solar system, stars and accretion disks -- from the single viewpoint of MHD. This approach provides effective methods and insights for the interpretation of plasma phenomena on virtually all scales, from the laboratory to the Universe. It equips the reader with the necessary tools to understand the complexities of plasma dynamics in extended magnetic structures. The classical MHD model is developed in detail without omitting steps in the derivations, and problems are included at the end of each chapter. This text is ideal for senior-level undergraduate and graduate courses in plasma physics and astrophysics.

CONTENTS Part I. Plasma Physics Preliminaries: 1. Introduction; 2. Elements of plasma physics; 3. 'Derivation' of the macroscopic equations; Part II. Basic Magnetohydrodynamics: 4. The MHD model; 5. Waves and characteristics; 6. Spectral theory; 7. Waves and instabilities on inhomogeneous plasmas; 8. Magnetic structures and dynamics; 9. Cylindrical plasmas; 10. Initial value problem and wave damping; 11. Resonant absorption and wave heating; Appendices.

ISBN 0521 6 2347 2 (hardback)   
ISBN 0 521 62607 2 (paperback)

Publications

Publications Goedbloed et al.: 
Publications.pdf (updated 5 June 2024)

Lectures

Lectures at Astronomy Department, University of Sao Paulo, March-May 2007

Miscellaneous