Book contents
- Frontmatter
- Dedication
- Contents
- Preface
- 1 Introduction
- 2 Characteristic Parameters of a Plasma
- 3 Single-Particle Motions
- 4 Waves in a Cold Plasma
- 5 Kinetic Theory and the Moment Equations
- 6 Magnetohydrodynamics
- 7 MHD Equilibria and Stability
- 8 Discontinuities and Shock Waves
- 9 Electrostatic Waves in a Hot Unmagnetized Plasma
- 10 Waves in a Hot Magnetized Plasma
- 11 Nonlinear Effects
- 12 Collisional Processes
- Appendix A Symbols
- Appendix B Useful Trigonometric Identities
- Appendix C Vector Differential Operators
- Appendix D Vector Calculus Identities
- Index
- References
8 - Discontinuities and Shock Waves
Published online by Cambridge University Press: 16 March 2017
Book contents
- Frontmatter
- Dedication
- Contents
- Preface
- 1 Introduction
- 2 Characteristic Parameters of a Plasma
- 3 Single-Particle Motions
- 4 Waves in a Cold Plasma
- 5 Kinetic Theory and the Moment Equations
- 6 Magnetohydrodynamics
- 7 MHD Equilibria and Stability
- 8 Discontinuities and Shock Waves
- 9 Electrostatic Waves in a Hot Unmagnetized Plasma
- 10 Waves in a Hot Magnetized Plasma
- 11 Nonlinear Effects
- 12 Collisional Processes
- Appendix A Symbols
- Appendix B Useful Trigonometric Identities
- Appendix C Vector Differential Operators
- Appendix D Vector Calculus Identities
- Index
- References
Summary
Discontinuities are a common feature of plasmas, especially in space and astrophysical applications where large spatial scales are involved. These discontinuities arise from a process called “wave steepening,” wherein nonlinear effects cause a wave to steepen into a discontinuity, the thickness of which is controlled by some microscopic scale length of the plasma, such as an ion cyclotron radius. Several types of discontinuities are discussed, the most important of which is a shock wave. In a shock wave the flow velocity suddenly changes from supersonic to subsonic at the discontinuity, with a corresponding increase in the plasma density and magnetic field strength. A detailed derivation of the equations that determines the propagation speed of a MHD shock wave is given, including the limiting cases of weak and strong shocks. The mechanisms by which shocks can accelerate particles to very high energies are discussed. These include shocks from solar coronal mass ejections, which are known to accelerate charged particles to energies of many tens of MeV, and shocks produced by supernovae explosions, which are believed to be responsible for the acceleration of cosmic rays to extremely high energies, 1014 eV or more.
- Type
- Chapter
- Information
- Introduction to Plasma PhysicsWith Space, Laboratory and Astrophysical Applications, pp. 281 - 318Publisher: Cambridge University PressPrint publication year: 2017
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