|Assessment Type||Assessment length / details||Proportion|
|Semester Assessment||3 Hours Written Examination||70%|
|Semester Assessment||Assignments Sheets||30%|
|Supplementary Assessment||3 Hours Written Examination||100%|
On successful completion of this module students should be able to:
1. Describe the fundamental characteristics of plasmas.
2. Discuss the behaviour of plasmas from the standpoints of both individual particles and bulk fluid-like properties.
3. Explain the properties of certain types of waves and instabilities in plasmas.
4. Discuss the formation of shocks in a collisionless medium
5. Discuss the physical processes governing the production and loss of ionisation in an atmosphere
6. Explain the characteristics of different ionospheric layers in terms of the variation with height of the production, loss and transport mechanisms
7. Describe the role of ionospheric and thermospheric chemistry in determining the characteristics of the ionosphere near the F-layer peak
8. Outline the principles of propagation of radio waves in an ionised medium and from them derive the principles of radio sounding
9. Discuss the principles of incoherent scatter radar and how it can be used to study the ionosphere
10. Understand the solar-terrestrial coupling processes and their effects on the ionosphere and magnetosphere
11. Describe the process of magnetic reconnection
12. Discuss the motion of particles in 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.
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.
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. Solar wind-magnetosphere coupling; magnetic reconnection. Plasma convection. Electric currents; Pedersen, Hall, field-aligned. High-latitude ionosphere coupling to Magnetoshpere, auroral electrojets, geomagnetic substorms, aurora.
This module is at CQFW Level 6