Speaker
Dr
Mikhail Viktorov
(Institute of Applied Physics of Russian Academy of Sciences)
Description
Study of plasma instabilities in the electron cyclotron frequency range, which were carried out over the last decade at the IAP RAS (Nizhny Novgorod), has resulted in a significant progress in understanding the nature of these processes. The object of our research activities is the nonequilibrium plasma created and sustained by powerful radiation of a gyrotron (80 kW @ 37.5 GHz) under the electron cyclotron resonance (ECR) condition. ECR plasma heating allows to create plasma with at least two electron components, one of which, more dense and cold, determines the dispersion properties of the high-frequency waves, and the second, a small group of energetic electrons with a highly anisotropic velocity distribution, is responsible for the excitation (and absorption) of the unstable waves. The interaction of high-frequency waves with resonant electrons leads to the diffusion of energetic electrons in velocity space and eventually to their falling into the loss cone and precipitation from the trap. In the experiments we studied the dynamic spectrum and the intensity of stimulated electromagnetic radiation from the plasma with high temporal resolution (up to 10 ps). This technique allowed to explore the fine structure in the spectrum of excited waves.
Different conditions for instability development are implemented at three ECR discharge stages. The parameter scan is performed due to the plasma density variation in the ECR discharge. At the initial discharge stage dense plasma component is almost absent and a fast extraordinary wave can be excited. At a large density of the background plasma during the developed discharge phase cyclotron instabilities of extraordinary modes are suppressed and the whistler mode instability is observed. In a decaying plasma after the ECR heating switch-off loss-cone instabilities of the extraordinary waves are observed. Under the certain conditions the excitation of plasma waves under the double plasma resonance is observed at the very beginning of plasma decay stage. Eventually, we defined at least five different types of kinetic instabilities observed in the ECR discharge plasma.
Theoretical interpretation of the observed data is based on the balance maser equations for evolution of hot electron density and the density of electromagnetic energy. Taking into account the plasma parameters at different discharge stages, this approach allows us to reproduce temporal features of the observed instabilities and estimate its growth rates.
This report may be of interest in the context of a laboratory modeling of nonstationary wave-particle interaction processes in nonequilibrium space plasma since the observed phenomena have much in common with similar processes occurring in the magnetosphere of the Earth, planets, and in solar coronal loops.
Primary author
Dr
Mikhail Viktorov
(Institute of Applied Physics of Russian Academy of Sciences)
Co-authors
Prof.
Alexander Shalashov
(Institute of Applied Physics of Russian Academy of Sciences)
Dr
Alexander Vodopyanov
(Institute of Applied Physics of Russian Academy of Sciences)
Dr
Dmitry Mansfeld
(Institute of Applied Physics of Russian Academy of Sciences)
Dr
Egor Gospodchikov
(Institute of Applied Physics of Russian Academy of Sciences)
Prof.
Sergey Golubev
(Institute of Applied Physics of Russian Academy of Sciences)
Prof.
Valery Zaitsev
(Institute of Applied Physics of Russian Academy of Sciences)
