Gwybodaeth Modiwlau

The course covers the essentials of plasma physics, including the nature of a plasma, motion of single charged particles in a magnetic field, magnetohydrodynamics, waves in plasma, and instabilities. The theory will be illustrated by examples from interplanetary space and the magnetosphere.
The presence of ionisation in the upper atmosphere was postulated to account for long distance radio wave propagation. Subsequent research established the existence of the ionosphere. Active research continues to study ionospheric plasma processes in terms of solar-terrestrial interactions, in particular at high latitudes where the aurorae are a spectacular optical manifestation of incoming particles from space.
The morphology of the ionosphere is described, the production and loss processes of ionisation under normal conditions are explained, and the effects of neutral winds and electric fields are considered. An introduction is given to the influence of the ionosphere on radiowaves. The coupling of the solar wind to the Earth's magnetoshphere is discussed and the consequences on the ionosphere described.

Plasma Physics
Occurrence of plasmas, temperature of a plasma, Debye shielding, plasma oscillations. Motion of a single charged particle in (a) a homogenous magnetic field; gyro-radius and frequency; (b) a converging magnetic field; magnetic mirror; (c) an inhomogenous magnetic field; drift motion (d) a magnetic field with a perpendicular electric field.
Space Plasmas, waves and shocks
Magnetohydrodynamics: Maxwell's equations applied to a plasma; diffusion time of magnetic field in a plasma; "frozen-in" fields, magnetic Reynold's number. Waves in a plasma: electron plasma waves, ion-acoustic waves, MHD waves, shear Alfven waves, fast-mode (compressional) waves. Collisionless shocks. Types of instability, two-stream instability (simple "doppler-shift" treatment), Rayleigh-Taylor and Kelvin-Helmholtz instabilities (qualitative treatment).
The ionosphere at mid and low latitudes: D, E and F regions, ionisation production and loss mechanisms, Chapman layers. Transport of ionisation and the formation of the F2 peak. Ionospheric chemistry and the physical basis of anticorrelations between electron temperature and density. Ionospheric dynamics and the servo-theory of the F-region..
Experimental techniques: Radiowave propagation: plasma frequency, gyrofrequency, phase velocity, group velocity, refractive index. The Appleton-Hartree equation and radio sounding. Incoherent scatter and ionospheric radar.
The High-Latitude Ionosphere and the Magnetosphere: Magnetoscopic regions. Geomagnetic field; dipolar and distorted. Motion of charged particles; gyro, bounce and drift motion. Soalr wind-magnetosphere coupling; magnetic reconnection. Plasma convection. Electric currents; Pedersen, Hall, field-aligned. High-latitude ionosphere coupling to Magnetoshpere, auroral electrojets, geomagnetic substorms, aurora.