Experiments showing the dynamics in the self-organization of surface wave sustained discharges are presented. Microwave ͑2.4 GHz͒ discharges maintained in an argon gas in a continuous wave regime at a constant applied power and varying gas pressure are studied. The evolution of the discharge from a stationary plasma column at comparatively low pressure (pр10 Torr) to a plasma torch at atmospheric pressure passes through different stages of self-organization of the wave-field↔plasma nonlinear structure showing evidence of the general trends of behavior of nonequilibrium dissipative systems. The measurements are carried out at the stage of the discharge self-organization into a filamentary structure with an azimuthal rotation. Macroscopic characteristics ͑number, size, velocity of rotation͒ of the filaments and their dependence on the gas pressure and its time variation are given. The total light emission of the plasma considered as giving information about the plasma density is measured and different methods of signal processing ͑including correlation-spectrum analysis͒ are applied. Oscillations of the filament ends are also observed. The different types of interrelation between plasma density and field intensity, registrated in the different pressure ranges, call for variety in the instability mechanisms. Although the scenario of the discharge self-organization is stressed in the discussions, the observations are important with their relation to the discharge applications, which require avoiding conditions of development of instabilities.
Theoretical studies of electric current instability explaining solar prominence eruptions show that the loss of equilibrium may develop in a case when the surrounding magnetic field decreases sufficiently rapidly with height. The magnetic decay index, a parameter indicating whether the external magnetic field has a configuration that may lead to a certain type of electric current instability, is a useful instrument for predicting the behavior of prominences. In our study, we consider three eruptive prominences. We perform potential-field extrapolation to obtain the spatial distribution of the magnetic decay index in the coronal space identified with the prominences. Analysis of time-dependent height profiles of the prominences revealed that eruptions started at heights close to those, where the computed magnetic decay index exceeded a value equal to 1.5. This indicates that the torus instability is a possible mechanism of the considered eruptive events.
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