Book contents
- Frontmatter
- Contents
- Preface
- Part I Theoretical Description of Gases and Plasmas
- Chapter 1 Particle Orbit Theory
- Chapter 2 Kinetic Theory
- Chapter 3 Basic Plasma Phenomena
- Chapter 4 Fluid and MHD Theory
- Chapter 5 Waves and Oscillations
- Chapter 6 Shocks and Discontinuities
- Chapter 7 Transport of Superthermal Particles
- Part II The Upper Atmosphere
- Part III Sun—Earth Connection
- Appendices
- Bibliography
- Index
Chapter 2 - Kinetic Theory
Published online by Cambridge University Press: 22 October 2009
- Frontmatter
- Contents
- Preface
- Part I Theoretical Description of Gases and Plasmas
- Chapter 1 Particle Orbit Theory
- Chapter 2 Kinetic Theory
- Chapter 3 Basic Plasma Phenomena
- Chapter 4 Fluid and MHD Theory
- Chapter 5 Waves and Oscillations
- Chapter 6 Shocks and Discontinuities
- Chapter 7 Transport of Superthermal Particles
- Part II The Upper Atmosphere
- Part III Sun—Earth Connection
- Appendices
- Bibliography
- Index
Summary
Maxwell's velocity distribution function together with Clausius's mean free path concept were the key elements that made it possible to develop connections between the motions of microscopic molecules (molecules are defined in a very broad sense here, referring to any neutral or charged particle composing the gas) and the macroscopic properties of gases (observable by the methods of classical physics).
In this chapter we introduce some fundamental concepts of kinetic theory. For more details we refer the reader to books on classical kinetic theory (cf. Gombosi 1994).
Collisions
First, we introduce several statistical quantities such as the mean free path, collision frequency, collision rate, collision cross section, and differential cross section. We shall also see that these quantities are closely related to each other and to other fundamental molecular quantities. We will use very simple physical models to emphasize the basic concepts behind these new statistical quantities.
Mean Free Path
The free path is the distance traveled by a molecule between two successive collisions. The mean free path is the average distance between two successive collisions of a single molecule.
Consider a single molecule with velocity v. Assume that this particle suffers a collision with another molecule at a distance of s = 0. Let Ppath(s) denote the probability that this molecule survives a distance s without suffering a second collision.
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- Physics of the Space Environment , pp. 30 - 52Publisher: Cambridge University PressPrint publication year: 1998