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Kyuregyan A.S.,All Russia Institute of Electrical Engineering
Journal of Experimental and Theoretical Physics | Year: 2012

The transverse instability of a plane front of fast impact ionization waves in p +-n-n + semiconductor structures with a finite concentration of donors N in the n layer has been theoretically analyzed. It is assumed that the high velocity u of impact ionization waves is ensured owing to the avalanche multiplication of the uniform background of electrons and holes whose concentration σ b ahead of the front is high enough for the continuum approximation to be applicable. The problem of the calculation of the growth rate s of a small harmonic perturbation with wavenumber k is reduced to the eigenvalue problem for a specific homogeneous Volterra equation of the second kind containing the sum of double and triple integrals of an unknown eigenfunction. This problem has been solved by the method of successive approximations. It has been shown that the function s(k) for small k values increases monotonically in agreement with the analytical theory reported in Thermal Engineering 58 (13), 1119 (2011), reaches a maximum s M at k = k M, then decreases, and becomes negative at k > k 01. This behavior of the function s(k) for short-wavelength perturbations is due to a decrease in the distortion of the field owing to a finite thickness of the space charge region of the front and "smearing" of perturbation of concentrations owing to the transverse transport of charge carriers. The similarity laws for perturbations with k ≥ k M have been established: at fixed σ b values and the maximum field strength on the front E 0M, the growth rate s depends only on the ratio k/N and the boundary wavenumber k 01 ∞ N. The parameters s M, k M, and k 01, which determine the perturbation growth dynamics and the upper boundary of the instability region for impact ionization waves, have been presented as functions of E 0M. These dependences indicate that the model of a plane impact ionization wave is insufficient for describing the operation of avalanche voltage sharpers and that fronts of fast streamers in the continuum approximation should be stable with respect to transverse perturbations in agreement with the previously reported numerical simulation results. The results have been confirmed by the numerical simulation of the evolution of small harmonic perturbations of the steady-state plane impact ionization wave. © Pleiades Publishing, Inc., 2012.

Kyuregyan A.S.,All Russia Institute of Electrical Engineering
Journal of Experimental and Theoretical Physics | Year: 2010

The existence of generalized self-similar solutions to the system of continuity and Poisson equations is analyzed for the problem of evolution of impact ionization waves (IIWs). It is shown that, for any physically reasonable electric-field dependence of the impact ionization coefficients, there exist only exponentially self-similar ("limiting") asymptotic solutions. These solutions describe IIWs whose spatial scales and propagation velocities increase exponentially with time. Conditions are found for the existence of plane, cylindrical, and spherical waves of this type; their structure is described; analytical relations between the key parameters are derived; and effects of recombination (or attachment) and tunnel ionization are analyzed. It is shown that these IIWs are intermediate asymptotics of numerical solutions to the corresponding Cauchy problems. The most important and interesting type of exponentially self-similar IIWs are streamers in a uniform electric field. The simplest comprehensive and explicit model describing their evolution is a spherical IIW. © Pleiades Publishing, Inc., 2010.

Kostinskiy A.Y.,RAS Institute of Applied Physics | Syssoev V.S.,RAS Institute of Applied Physics | Bogatov N.A.,RAS Institute of Applied Physics | Mareev E.A.,RAS Institute of Applied Physics | And 4 more authors.
Geophysical Research Letters | Year: 2015

We have observed unusual plasma formations (UPFs) in artificial clouds of charged water droplets using a high-speed infrared camera operating in conjunction with a high-speed visible-range camera. Inferred plasma parameters were close to those of long-spark leaders observed in the same experiments, while the channel morphology was distinctly different from that of leaders, so that UPFs can be viewed as a new type of in-cloud discharge. These formations can occur in the absence of spark leaders and appear to be manifestations of collective processes building, essentially from scratch, a complex hierarchical network of interacting channels at different stages of development (some of which are hot and live for milliseconds). We believe that the phenomenon should commonly occur in thunderclouds and might give insights on the missing link in the still poorly understood lightning initiation process. Key Points High-speed infrared images allowed us to discover a new type of in-cloud discharges These discharges (UPFs) can occur both with and without spark UPF morphology is distinctly different from that of leaders © 2015. American Geophysical Union. All Rights Reserved.

Kostinskiy A.Y.,RAS Institute of Applied Physics | Syssoev V.S.,RAS Institute of Applied Physics | Bogatov N.A.,RAS Institute of Applied Physics | Mareev E.A.,RAS Institute of Applied Physics | And 4 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2015

Detailed infrared (2.7-5.5 μm) images of bidirectional leaders produced by the cloud of small (typical radius of 0.5 μm), positively charged water droplets are presented. The leader was composed of the downward extending positive part and the upward extending negative part, these two parts (both branched, although in different ways) being connected by the single-channel middle part. The downward extending part included the tortuous positive leader channel (similar to its upward extending counterpart observed when the cloud polarity was negative) that was often accompanied by much less tortuous but often equally bright downward extending plasma formations of unknown nature. Very faint positive streamer zone was also observed. Either the positive leader channel or the unusual plasma formation (UPF) can come in contact with the grounded plane. The upward extending part is associated with a large network of faint channels, mostly fanning out of the upper part of the usually much brighter leader channel and apparently pervading the entire upper part of the cloud. Some of those faint channels could be unusually long and bright negative streamers, while others could be similar to UPFs. The IR luminosity along the brightest part of the bidirectional leader channel is often nonuniform. Some variations in channel brightness are localized and suggest the involvement of space leader-type processes at multiple positions along the channel, changes in channel orientation, or variations in channel radius. © 2015. American Geophysical Union. All Rights Reserved.

Kostinskiy A.Y.,National Research University Higher School of Economics | Syssoev V.S.,RAS Institute of Applied Physics | Mareev E.A.,RAS Institute of Applied Physics | Rakov V.A.,University of Florida | And 7 more authors.
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2015

The possibility of initiation of electric discharges by a crossbow bolt (projectile) moving in the electric field of a cloud of negatively charged water droplets has been demonstrated for the first time. Over one hundred of discharges have been produced. For each event, a high-speed video camera recorded the images of upward positive leaders developing from both the nearby grounded sphere and the projectile, followed by the return-stroke-like process. Corresponding currents were measured and integrated photos of the events were obtained. The results can help to improve our understanding of lightning initiation by airborne vehicles and by a vertical conductor rapidly extended below the thundercloud in order to trigger lightning with the rocket-and-wire technique. © 2015.

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