ABSTRACT
The problem of electric double layers in a plasma is now an object of intense experimental and theoretical investigation. This attention was stimulated by the fact that electric double layers are a candidate for a very probable mechanism of the discrete aurora borealis, which is an immensely intriguing natural phenomenon. This chapter discusses the simplest situation, in which only two groups of charged particles participated in the formation of the double layer: free electrons and free ions. The formation of double layers is connected, among other things, with the Pierce and Budker-Buneman instabilities and also with the dynamics of the arising virtual cathode. If, however, the beam current is greater than the random current of plasma electrons, then two double layers appear in the system: one close to the cathode and the other in the region of the virtual cathode.
