## ASTM116 Astrophysical Plasmas

**Course Programme**:

1 Introduction

What is a Plasma?

Examples of astrophysical plasmas.

Governing equations.

Some basic plasma phenomena: quasi-neutrality, plasma oscillations, collisions.

2 Particle motion in electro-magnetic fields

Motion of charged particle in electro-magnetic fields, introducing:

Particle gyration.

Gyro- (or cyclotron) frequency, Larmor radius (or gyro-radius).

Particle motion in combined uniform, static electric and magnetic fields.

Particle drifts.

Motion in non-uniform magnetic field, magnetic mirror, magnetic moment.

Applications of particle motion to energetic particles in the Earth's magnetosphere (the radiation, or Van Allen belts), radio emission from jets in radio galaxies, particle acceleration, etc.

3 One fluid magnetohydrodynamics (MHD)

Plasma described as a highly conducting fluid, introducing:

Basic MHD equations.

Induction equation for evolution of magnetic field.

Ideal MHD and flux "freezing".

Magnetic diffusion, magnetic Reynold's number.

"Cell" picture of plasma universe.

Electromagnetic forces in MHD

Flux tubes

MHD Waves and Instabilities

The Dynamo Problem

4 The Solar Wind

What is the solar wind, and how is it measured?

A simple model for generation of solar wind.

Effect of solar rotation on interplanetary field.

Observations of the solar wind: waves, shocks, effects of solar activity, etc.

The solar-terrestrial connection.

5 Magnetic Reconnection

The conversion of magnetic energy to other forms, and the role of reconnection to change the topology of magnetic field lines.

Current sheets and magnetic annihilation.

Sweet-Parker model of steady reconnection.

Petschek and other more realistic reconnection models.

Application of magnetic reconnection to planetary magnetospheres (geomagnetic storms), and solar/stellar activity (flares, coronal heating etc).

6 Two-fluid Magnetohydrodynamics

Two-fluid equations

High-frequency waves in cold plasmas

7 Particle Acceleration at Shocks

The formation of shocks in supersonic flows, the role of shocks in converting flow energy to heat and particle acceleration, collisionless shocks, and importance of shocks to explain observations of accelerated particles

Elementary introduction to shock conservation equations.

Shock (magnetic) geometry (perpendicular/parallel).

Different types of shock structure.

Shock drift acceleration.

Diffusive (or Fermi) shock acceleration.

Astro-Plasmas (additional notes):

ASTM 116 2006 Exam

[ **Back to Physics lectures** ]