Astrophysical magnetic fields essentials

This is the set of viewgraphs

F. Cattaneo

Brief overview of magnetic fields in the Universe:

Typical intensities and morphologies.

Magnetic fields of planets, stars, compact object, galaxies, interstellar medium, etc.

Brief overview of magnetic environments:

Stellar interiors, stellar atmospheres, interstellar medium, accretion discs, etc.

Typical plasma parameters: densities, temperatures, collisionality.

Description of magnetized plasmas:

Kinetic description: Vlasov equation.

Continuum description: Moments, two-fluids equations, MHD.

High conductivity limit:

Ideal MHD. Alfvén theorem. Consequences of the “frozen in” condition: field advection and distortion.

MHD invariants: Energy, helicity, cross helicity.

Simple solutions: MHD waves, magnetostatic equilibria, formation of singularities.

Non ideal effects:

Ohm’s law, and its generalizations.

Reconnection: Sweet-Parker reconnection, Hall-term effects, collisionless reconnection.

Dynamo action: generation of small-scale fields. Kazatsev model and its generalizations. Generation of large-scale fields and Mean Field Electrodynamics. The alpha and omega effects.

MHD turbulence. The energy cascade. Critical balance. Spontaneous alignment. The spectrum of MHD turbulence.