A Hybrid Mode and a Classification of Beam Plasma Instabilities
Abstract
The interactions of an electron beam with a background plasma are classified according to the beam energy and to the relative density of the beam and the plasma. Both the electron beam and plasma are assumed to be cold, unmagnetized, collisionless, and all equilibrium self-fields have been assumed negligible. Emphasis is placed on the dynamical coupling of longitudinal and transverse motions as a result of relativistic and electromagnetic effects. Over many orders of magnitudes, we find that the parameter space may be divided into just a few domains, with different instability mechanisms. The boundaries separating these domains are given, together with the instability growth rates and the characteristic wave number of the instability within each of these domains. This classification thus provides and immediate assessment of the nature specified. In addition to the classical two stream instabilities and the Weibel type instabilities, a new mode, temporarily called the hybrid mode, is discovered: The hybrid mode is dominant when the electron beam is highly relativistic. We provide several examples of current interest to demonstrate the use of this classification. The results have been tested against the dispersion relationship given by Tajima, Jones and Shoucri. Effects of a finite beam are discussed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 11, 1985
- Accession Number
- ADA157356
Entities
People
- Yueying Lau
Organizations
- United States Naval Research Laboratory