The second part of this book is concerned with elementary physical processes involved in studies of high energy phenomena in the Universe. There are many excellent books which discuss this material at various levels of sophistication. Those which I have found most helpful are Jackson's Classical Electrodynamics (Jackson, 1999), Radiation Processes in Astrophysics by Rybicki and Lightman (1979) and Electromagnetic Processes by Gould (2005). Zombeck's Handbook of Space Astronomy and Astrophysics (Zombeck, 2006) contains a very useful compendium of relevant data.

My intention is to emphasise the underlying physical principles involved in these processes so that the functional forms of the equations have an intuitive significance. I will build up each discussion gently, often deriving approximate results which give physical insight before deriving, or quoting, the results of more complete calculations. I will treat the key processes of synchrotron radiation and inverse Compton scattering in some detail.

In the various calculations and derivations, I use Système International (SI) units, which have been officially adopted by almost all countries in the world. According to the Wikipedia web site (2008), ‘Three nations have not officially adopted the International System of Units as their primary or sole system of measurement: Liberia, the Union of Myanmar (Burma) and the United States.’