RadiophyJies and Quantum Electronics, Vol. ,~0, 17o. 5, 1997 ON THE EFFECT OF BUM GENERATION ENHANCEMENT REVEALED USING THE SCHEME OF ADDITIONAL HEATING OF IONOSPHERIC PLASMA V. L. Frolov, L. M. Erukhimov, G. P. Komrakov, E. N. Sergeev, B. Thidd, P. A. Bernhardt, L. S. Wagner, J. A. Goldstein, and G. Selcher UDC 533.951, 537.868 We present measured characteristics of the artificial ionospheric radio emission (AIRE), which were obtained ~perimentally e.sing additional heating of the ionospheric F-region by O-polarized waves. It is shown that the observed enhancement of intensity of the broad upshifled mazimura (BUM) of the AIRE can resnlt from the influence of electrons accelerated in the plasma: esonance regmn on its generation. An empirical model of the phenomenon observed is developed. It is concluded from ezperimental results that the BUM has a complez structure and only one of its components produces the above emission enhancement. We show the possibility of using the AIRE in additional heating of ionospheric plasma for diagnostics of artificial ionospheric turbulence and investigation of the features of perturbation propagation along the geomagnetic field lines. INTRODUCTION A long-term (more than 1.5 decades) and intense study of the characteristicsof the artificial ionospheric radio emission (AIRE) induced by a high-power O-polarized wave near itsreflectionpoint allows us to single out and investigateindividual components in itsspectrum and construct empirical and theoretical(for some components) models of their generation. Primarily, this refers to such usually observed AIRE components as downshifted maYirnum (DM) [I-7],broad continuum (BC) [2, 3, 5-7], narrow continuum (NC) [5-8], and broad upshifted ma~rrmm (BUM) whose generation is observed when the pump wave PW frequency is slightly greater than the gyroresonance harmonic frequency [1, 6, 7, 9-12]. The A/RE characteristic sensitivity to variation of the interaction conditions between a PW and plasma determines the important role it has been playing in recent years as one of the basic methods of diagnostics of processes that occur in the ionosphere modified by a high-power wave. Long ago it was proposed to use the AIRE as a means of diagnostics of artificial ionospheric turbulence (AIT). We must emphasize [1], in which the possibility of studying the properties of different types of parametric instabilities is considered, [3, 13, 14], in which a method for measuring characteristics of the development of small-scale artificial ionospheric irregularities (SSAII) is proposed using the AIRE, and [15- 17], in which a method for measuring the times of development and relaxation of a high-frequency plasma turbulence (HFPT) is worked out on the basis of measuring emission evolution characteristics. Recent studies of AIT diagnostics have widely used additional ionospheric heating by a second high-power radio wave [3, 7, 13, 14, 27, 52], which allows us in some cases to single out and study in detail the influence of a certain parameter of plasma or its perturbation on development of the interaction between the plasma and a high-power electromagnetic wave. In this paper, we consider the results of experimental studies of BUM generation enhancement reported in [18] under additional heating of the ionospheric plasma by a second high-power O-polarized radio wave. Radiophysical Research Institute, Nizhny Novgorod, Russia. Institute of Space Physics, Uppsala, Sweden. The Naval Research Laboratory, Washington, D.C. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radlofizika, Vol. 40, No. 5, pp. 561-585, May, 1997. Original article submitted October 15, 1996. 0033-8443/97/4005-0371518.00 (~)1998 Plenum Publishing Corporation 371