Electric discharges produced by clouds of charged water droplets in the presence of moving conducting object
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.
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.
Particles interaction and value of the screening length in dusty plasma systems are of great interest in dusty plasma area. Three inter-particle potentials (Debye potential, Gurevich potential and interaction potential in the weakly collisional regime) are used to solve equilibrium equations for two dusty particles suspended in a parabolic trap. The inter-particle distance dependence on screening length, trap parameter and particle charge is obtained. The functional form of inter-particle distance dependence on ion temperature is investigated and compared with experimental data at 200–300 K in order to test used potentials applicability to dusty plasma systems at room temperatures. The preference is given to the Yukawa-type potential including effective values of particle charge and screening length. The estimated effective value of the screening length is 5–15 times larger than the Debye length.
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.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.