Lecture

Magnetohydrodynamics: Modeling and Equations

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In course

PHYS-325: Introduction to plasma physics

Introduction à la physique des plasmas destinée à donner une vue globale des propriétés essentielles et uniques d'un plasma et à présenter les approches couramment utilisées pour modéliser son comportement. Application à la fusion thermonucléaire ainsi qu' ...

Description

This lecture introduces the physics of plasmas, focusing on magnetohydrodynamics (MHD). The instructor covers the two-fluid model, MHD equations, conservation of energy, Alfvén's theorem, solar wind, Parker spiral, magnetic reconnection, dynamos, and MHD waves. The lecture discusses the challenges of modeling plasmas, including the impossibility of Maxwell's equations. Various scales, from particle number to spatial dimensions, are explored, with a focus on ITER. The lecture also delves into the equations of state, continuity, and closure in the two-fluid model, emphasizing the conservation of mass. The Alfven theorem, magnetic field dynamics, and collisional effects are discussed in the context of MHD.

Instructors (2)

Stefano Alberti

Teaching & PhD Past EPFL PhD Students Gilles Arnoux, Falk Braunmüller, Jérémy Genoud

Joaquim Loizu Cisquella

Joaquim Loizu graduated in Physics at the École Polytechnique Fédérale de Lausanne, carrying out his Master thesis project at the Center for Bio-Inspired Technology, Imperial College London, on the theoretical and numerical study of the biophysics of light-sensitive neurons. In 2009, he started his PhD studies with Prof. Paolo Ricci at the Swiss Plasma Center, the major plasma and fusion laboratory in Switzerland. His thesis focused on the theory of plasma-wall interactions and their effect on the mean flows and turbulence in magnetized plasmas. He obtained his PhD in December 2013. In 2014, he joined the Max-Planck-Princeton Center for plasma research as a Postdoctoral Research Fellow, spending one year at the Princeton Plasma Physics Laboratory and one year at the Max-Planck-Institute for Plasma Physics in Greifswald, Germany. During this time, he worked on three-dimensional magnetohydrodynamics, studying the formation of singular currents and magnetic islands at rational surfaces. In 2016, he obtained a two-years Eurofusion Postdoctoral Fellowship to carry out research at the Max-Planck-Institute for Plasma Physics in Greifswald, Germany. During this time, he focused on the computation of 3D MHD equilibria in stellarators, including the possibility of magnetic islands and magnetic field-line chaos. In 2018, he joined the Swiss Plasma Center as a Scientist and Lecturer. He is also one of the leaders of the Simons Collaboration on Hidden Symmetries and Fusion Energy. His current research interests include MHD equilibrium and stability, magnetic reconnection, self-organization, non-neutral plasmas, plasma sheaths, and plasma transport in chaotic magnetic fields.

Official source

Ontological neighbourhood

Physics

Plasma physics: Space-plasma physics

Related concepts (32)

Coronal seismology

Coronal seismology is a technique of studying the plasma of the Sun's corona with the use of magnetohydrodynamic (MHD) waves and oscillations. Magnetohydrodynamics studies the dynamics of electrically conducting fluids - in this case the fluid is the coronal plasma. Observed properties of the waves (e.g. period, wavelength, amplitude, temporal and spatial signatures (what is the shape of the wave perturbation?), characteristic scenarios of the wave evolution (is the wave damped?), combined with a theoretical modelling of the wave phenomena (dispersion relations, evolutionary equations, etc.

Magnetohydrodynamics

Magnetohydrodynamics (MHD; also called magneto-fluid dynamics or hydromagnetics) is a model of electrically conducting fluids that treats all interpenetrating particle species together as a single continuous medium. It is primarily concerned with the low-frequency, large-scale, magnetic behavior in plasmas and liquid metals and has applications in numerous fields including geophysics, astrophysics, and engineering. The word magnetohydrodynamics is derived from magneto- meaning magnetic field, hydro- meaning water, and dynamics meaning movement.

Plasma stability

The stability of a plasma is an important consideration in the study of plasma physics. When a system containing a plasma is at equilibrium, it is possible for certain parts of the plasma to be disturbed by small perturbative forces acting on it. The stability of the system determines if the perturbations will grow, oscillate, or be damped out. In many cases, a plasma can be treated as a fluid and its stability analyzed with magnetohydrodynamics (MHD).

Interplanetary medium

The interplanetary medium (IPM) or interplanetary space consists of the mass and energy which fills the Solar System, and through which all the larger Solar System bodies, such as planets, dwarf planets, asteroids, and comets, move. The IPM stops at the heliopause, outside of which the interstellar medium begins. Before 1950, interplanetary space was widely considered to either be an empty vacuum, or consisting of "aether". The interplanetary medium includes interplanetary dust, cosmic rays, and hot plasma from the solar wind.

Magnetic reconnection

Magnetic reconnection is a physical process occurring in electrically conducting plasmas, in which the magnetic topology is rearranged and magnetic energy is converted to kinetic energy, thermal energy, and particle acceleration. Magnetic reconnection involves plasma flows at a substantial fraction of the Alfvén wave speed, which is the fundamental speed for mechanical information flow in a magnetized plasma. The concept of magnetic reconnection was developed in parallel by researchers working in solar physics and in the interaction between the solar wind and magnetized planets.

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