Apokamp Discharge Research Articles

Laboratory Simulation of the Effect of Volcanic Material on the Formation of Transient Phenomena Near the Boundary between the Middle and Lower Atmosphere

It is ascertained that heating of volcanic material from the Etna volcano (Italy) by an apokampic discharge reduces the voltage at which a positive streamer (apokamp) starts from the discharge channel and increases its propagation speed. The luminescence spectra show these processes to be accompanied by the emission of easily ionizable K and Na, which is consistent with data on the elemental composition of Etna samples. A hypothesis is suggested about an increase in the appearance probability of blue jets and starters over sites of high volcanic activity at altitudes of 10–18 km (at the level of the troposphere).

Моделирование транзиентных световых явлений средней атмосферы Земли c помощью апокампического разряда

Моделирование транзиентных световых явлений средней атмосферы Земли c помощью апокампического разряда

Experimental modelling of apokamp discharge formation under outer electric field

A laboratory setup has been created for modeling certain aspects of the initiation process of blue jets in the Earth’s atmosphere. With its help, the influence of an electric field on the apokamp discharge in air at pressures of 180-260 Torr was established. It is shown that the formation of a negatively charged zone located above the channel of a pulse-periodic discharge with a positive potential leads to both initiation and lengthening of the apokamps starting from the channel, and also reduces the voltage amplitude necessary for their formation.

Apokamp-type gas discharge phenomenon: Experimental and theoretical backgrounds

The apokamp discharge is an atmospheric pressure plasma jet generating from the bending point of the discharge channel between high-voltage and floating potential electrodes. The jet propagates perpendicularly to the interelectrode discharge channel for several centimetres without gas convection. Based on the simplified plasma-chemical model of the discharge, a theoretical explanation of the apokamp phenomenon was obtained for the first time. It is shown that the apokamp is a stable plasma quasi-jet formed by the positive streamer mechanism.

Laboratory Simulation of Blue Jets with Apokampic Discharge in the Hz Frequency Range

It is shown that the channel of apokampic discharge is a source of streamers at low air pressure and low frequencies (7–16 Hz) of high-voltage positive-polarity pulses and voltage amplitudes from 26 to 35 kV. The maximal starting speed of laboratory streamers was 560 km/s. A hypothesis about blue jet origination in nature is suggested based on experimental data. For their start, high frequencies of voltage pulses are not required, breakdowns in the Hz range are sufficient, but the discharge channel should bend and the field intensity should be high at the bending point.

Apokampic Discharge: Formation Conditions and Mechanisms

The experimental and theoretical investigations of a new form of burning of a repetitively-pulsed discharge – apokamp – are performed. It is shown that an apokampic discharge represents a narrow streamer channel, growing from the point of plasma channel bending, having a characteristic propagation velocity of tens and hundreds of meters per second, depending on the applied voltage and gas pressure and type. The conditions necessary for an apokamp to evolve are formed in a comparatively weak macroscopic electric field. The channel bend ensures a local field enhancement, which prescribes the starting orientation of the growing streamer channel. The pulse-frequency power supply regime of the discharge reproduces the streamer channel in every pulse, but the preceding framework of the ion-ion plasma ensures reproduction of the channel shape from pulse to pulse.

Апокампический разряд: условия образования и механизмы формирования

Апокампический разряд: условия образования и механизмы формирования

Laboratory modeling of blue jets with apokamp discharge in Hz frequency range

Laboratory modeling of blue jets with apokamp discharge in Hz frequency range

Radiation Intensity Profiles at Different Stages of the Formation of Apokamp Discharge

Experimental studies of the heat release processes in the apokamp discharge were carried out via the plotting of intensity charts. The procedure was verified with measurement techniques similar to those used in the operation of a disappearing filament pyrometer. A criterion was formulated for its applicability for the study of apokamp discharge in air. The intensity charts obtained at different stages of the formation of discharge confirm the need for gas heating near the discharge channel to form streamers.

The Influence of Molecular Gas on the Apokamp Discharge Formation

Emission spectra of apokamp discharge plasma jets in CO2, Ar, Kr, N2, and their mixtures have been studied. It has been shown that the emission spectra of the Kr–N2 mixture contain N2 and $$\rm{N_2^+}$$ bands, as well as Kr lines. The spectrum of the Ar–CO2 mixture is presented by bands of the Fox–Duffendack–Barker system and lines of the exited argon atom. In all gas media under study, the reduction of the molecular gas quantity leads to the transition from an apokampic discharge in the form of a diffusion jet developing from the current channel to a volume discharge with a strong transverse glowing. The experimental apparatus described in this work is proposed for use in laboratory investigations of spectral characteristics of transient luminous events observed in atmospheres of planets of the Solar System.

The Field Strength Necessary for the Formation of Blue Jets in the Middle Atmosphere

The formation of blue jets in air at low pressures is simulated using an apokamp discharge. The field strength is measured in the discharge channel. Assuming the applicability of similarity laws to gas discharges, the field strength in a storm cloud during the formation of blue jets is assessed to be from 6 × 1010 to 1.9 × 109 V/m, which is much higher than the values characteristic of the development of cloud-to-ground lightning discharges. A hypothesis is suggested that excess magnitudes of characteristic fields is among features of high-voltage pulsed discharge within a cloud, which results in the formation of blue jets at altitudes of about 12–18 km.

Production of nitrogen oxides in air pulse-periodic discharge with apokamp

The decomposition products of pulse-periodic discharge atmospheric pressure plasma in apokamp, diffuse and corona modes were determined by optical and chemical methods. It is shown that apokamp discharge formation starts at a critical value of dissipation power in a discharge channel. Simultaneously, due to the thermochemical reactions, plasma starts to efficiently produce nitrogen oxides.

The ratio of the intensities of 2P and 1P molecular nitrogen bands in apokamp discharge at different air pressures

The ratio of the intensities of 2P and 1P molecular nitrogen bands in apokamp discharge at different air pressures

On the physical nature of apokampic discharge

Experimental and theoretical investigations of a diffuse jet (streamer) of apokampic discharge are carried out for various values of air pressure. It is established experimentally that this regime of pulse-periodic discharge is formed stage by stage. At the first stage, in a microsecond discharge of a voltage pulse of positive polarity, a potential spark channel formed during the first pulses between two needle electrodes is transformed into a diffuse channel. At the second stage, a weakly glowing halo is formed near the discharge channel, and a bright offshoot arises near the bending point. Finally, at the third stage of discharge in the steadystate mode, for frequencies of a few to tens of kilohertz in each pulse, the offshoot becomes a source of plasma bullets (streamers) moving with a velocity of up to 200 km/s. As a result of simulation of a streamer in atmospheric pressure air under conditions corresponding to the experimental data, a propagation velocity of up to 400 km/s is obtained for the streamer. It is shown that the formation of a jet significantly depends on the air temperature.

Emission properties of apokamp discharge at atmospheric pressure in air, argon, and helium

Emission spectra of the plasma jet of apokamp discharge in air, helium, and argon are studied. Apokamp at atmospheric pressure is formed in the areas of strengthening of the electric field near the bends in the channel of the pulse-periodic discharge and is directed perpendicularly to the discharge channel. Apokamp consists of a bright narrow “appendage” connected with the discharge channel and with the diffuse jet emerging from the channel. It is shown that, in helium, the emission of the diffuse part of apokamp is dominated by N2 and N2 +, while emission of the “appendage” display lines and bands of He, N2, N2 +, O, and OH. In argon, emission spectra of the diffuse part of the plasma jets contain not only N2 and N2 +, but also Ar lines. It is assumed that the surrounding air plays an important role in the formation of the diffuse part of apokamp in helium and argon.

Formation of an Apokampic Discharge Under Atmospheric Pressure Conditions

A new phenomenon is observed in a spark discharge developing under normal conditions in air in a discharge circuit with a capacitive decoupling. It consists in the current channel bending becoming a source of a 4–6 cm long plasma jet directed across the channel. The phenomenon is termed an apokampic discharge or an apokamp. Its emission spectrum contains the bands of electron-vibration transitions from the second positive group of molecular nitrogen. The conditions of formation of an apokamp are experimentally determined. A conclusion is drawn that in order construct a physical model of an apokamp, one has to take into account: 1) the presence of a local gas overheating in the site of the current channel bending, 2) the similarity of the current and voltage time dependences in the corona discharge and in the current channel (becoming a source of an apokamp), and 3) the length of the apokamp plasma jet.

Phenomenon of apokamp discharge

A new phenomenon has been discovered where a bend of a plasma channel becomes of a source of one or several diffuse jets that have a length (at a given voltage) up to 4–6 cm and are directed across the plasma channel at a pulse-periodic spark discharge in air under normal conditions. The phenomenon is called apokamp discharge (apokamp). The spectrum of radiation of the apokamp includes primarily the bands of electron-vibrational transitions of the second positive system of molecular nitrogen. The conditions of the formation of apokamp have been experimentally revealed and it has been established that it consists of plasma bunches moving from the plasma channel at each pulse at a velocity of about 220 km/s.