This paper summarizes the studies of plasma kinetic instabilities in the electron cyclotron frequency range carried out over the last decade at the Institute of Applied Physics in Nizhny Novgorod. We investigate the nonequilibrium plasma created and sustained by high-power microwave radiation of a gyrotron under the electron cyclotron resonance condition. Resonant plasma heating results in the formation of 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 of unstable waves. Dynamic spectra and the intensity of stimulated electromagnetic emission are studied with high temporal resolution. Interpretation of observed data is based on the cyclotron maser paradigm, in this context, a laboratory modeling of non-stationary wave-particle interaction processes have much in common with similar processes occurring in the magnetosphere of the Earth, planets, and in solar coronal loops.

Kinetic instabilities of nonequilibrium plasma heated by powerful radiation of gyrotron in electron cyclotron resonance conditions and confined in a mirror magnetic trap are reported. Instabilities are manifested as the generation of short pulses of electromagnetic radiation accompanied by precipitation of hot electrons from magnetic trap. Measuring electromagnetic field with high temporal resolution allowed to observe various dynamic spectra of electromagnetic radiation related to at least five types of kinetic instabilities. This paper 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.

-Chirping frequency patterns have been observed in the electron cyclotron emission from strongly nonequilibrium plasma confined in a table-top mirror magnetic trap. Such patterns are typical for the formation of nonlinear phase space structures in a proximity of the wave-particle resonances of a kinetically unstable plasma, also known as the "holes and clumps" mechanism. Our data provides the first experimental evidence for acting of this mechanism in the electron cyclotron frequency domain.Introduction. -Resonant interaction of electromagnetic waves and charged particles plays an important role in the dynamics of magnetoactive plasma confined in space and laboratory magnetic traps. One of the most intriguing manifestations of such interaction is emission of broadband radiation with regular variations of dynamical spectra, e.g. quasi-periodic bursts with a frequency sweeping, resulting from the development of kinetic plasma instabilities. Such events are common features of experimental plasmas. Kinetic instabilities are caused by the presence of positive gradients in the velocity distribution of resonant particles, whose formation is universal for both space and laboratory plasma. In space magnetic traps, the sources of free energy are formed due to different acceleration mechanisms of particles, such as betatron acceleration, plasma-wave turbulence and magnetic reconnection. Under laboratory conditions, the energetic particles with an anisotropic velocity distribution can be formed due to the features of plasma heating, when the energy of the external source is embedded in a specific region of the phase space, such as provided by resonant cyclotron heating or neutral beam injection in magnetic fusion experiment. Spatial gradients can also result in instabilities of waves for which the diffusion in real space is coupled to the diffusion in velocity space due to conservation of invariants of particle motion in inhomogeneous systems energy; this type of instability is exploited in the so-called alpha channeling proposals [1,2]. As a rule, plasma confined in laboratory traps consists of at least two components, one

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A specific nonlinear regime of electron-cyclotron instability is discussed aimed at explaining the complex temporal patterns of stimulated electromagnetic radiation from a mirror trap with a non-equilibrium plasma typical of an ECR discharge. This regime is characterized by self-modulation of a plasma cyclotron maser due to coherent interference of two counter-propagating unstable waves with degenerate frequencies resulting in the spatial modulation of the amplification coefficient. The proposed simple theoretical model allows one to reproduce the multi-scale time behavior of quasiperiodic pulses of electromagnetic radiation and related precipitation of energetic electrons detected in a laboratory setup based on a magnetic mirror trap with a plasma sustained by mm-wave gyrotron radiation.