Nonlinear effects in the ionosphere (cross modulation of radio waves)
have been known since the 1930s. Only recently, however, has the rapid
increase in the power and directivity of the radio transmitters made it
possible to alter the properties of the ionosphere strongly and to
modify it artificially by applying radio waves. This has revealed a
variety of new physical phenomena. Their study is not only of scien-
tific interest but also undisputedly of practical interest, and is
presently progressing very rapidly. This monograph is devoted to an
exposition of the present status of theoretical research on this
problem. Particular attention is paid, naturally, to problems in the
development of which the author himself took part. It is my pleasant
duty to thank V. L. Ginzburg, L. P. Pitaevskii, V. V. Vas'kov, E. E.
Tsedilina, A. B. Shvartsburg, and Va. S. Dimant for useful discussions
and for valuable remarks during various stages of the work on the
problem considered in this book. Contents 1. Introduction . . . . . . .
. . . . . . . . . . . .