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Introduction
For a long time the ball lightning (BL) attracts attention of the investigators by extraordinary features of its behavior and by unusual characteristics of its tracks of effect on material objects. However attempts to clarify this phenomenon are complicated by occasional and transitory character of its appearance in the nature, by diversity and apparent inconsistency of the forms observed by the eyewitnesses. Also, the absence of reliable methods of its reproduction in the laboratory makes one to study similar but considerably less impressive effects.
We think that in the present situation the key moment is the realization of the fact that in BL investigations it is necessary to direct efforts to the laboratory experiments, because, on the one hand, they are capable to give effects, which, though being considerably weaker, are similar the naturally arising ones, and on the other hand, the laboratory experiments are carried out in controlled and reproducible conditions, which is the basis for researches advances. The reproducing of more stronger effects can be attained only as a result of a sure comprehension of the nature of effects obtained on the reached level of the researches followed by determination of directions for their perfecting.
To work out a method of creation of the artificial objects with sufficiently interesting properties it is necessary to draw attention to the physical conditions of the BL formation. We have extremely poor information about features of BL formation processes, so, concerning the existing hypotheses of BL nature, it remains only to discuss which of them are more or less probable. The experience of BL modeling gained at the previous investigations shows that if we have concentrated on improving of some parameter we obtain objects having only partial resemblance with BL. It seems, therefore, that the required physical conditions should represent a sensitive combination of rigid restrictions, characteristic features of these condition being high nonequilibrium and low stability.
Within the framework of the scientific approach, any attempt of reproduction of unexplored phenomenon requires sufficiently concrete supposition about its nature. Available on the present moment data admit to consider BL as a particular state of the matter whose the most essential feature consists in accumulation of energy, sufficiently exceeding the thermal one, with possibility of long and relatively stable conservation of this energy. Virtually, in this case we speak about metastable exited state of the matter keeping atoms or their part, without specification of the form of excitation energy and of the relative stability nature.
One of the principle form of energy contained in the matter is energy of electromagnetic fields of the nuclei and the electrons.According to the hypothesis of Bychkov V.L. [1], based on the electret physics, there exists a specific strongly charged state of dielectric substrate (in particular, polymer one) with estimated properties resembling BL. Another hypothesis, which is due to Manykin E.A. and co-authors [2], considers BL as metallic condensed state of the system of electron-excited atoms. In condensed disperse phase, dust plasma, and flame may exist high charged states of the particles, which in some cases take the form resembling BL. Note that in essence the chemical energy is also electrical. We suppose, that the electrical propinquity of all these forms of energy is the main cause of the existing resemblance between corresponding autonomous objects and the BL formations , the latter having especially strong electrical manifestations.
In this connection, among a great many of plasma physics
objects the high non-equilibrium dense plasma with condensed phase is of
special interest for experimental modeling of BL on small-size experimental
installations. At this plasma there exist practically the all mentioned
above forms of energy and the states of the matter, with active processes
of their interaction and mutual transformations. This gives the confidence
that, under the condition of right adjustment of the discharge mode, the
output objects should contain the matter approaching on its characteristics
to the BL matter.
Approach to creation of long-life plasma formations.
We think of the ball lightning (BL) with strong electrical manifestations as condensate of heavily excited states of multi-electron atoms [1,2]. We consider the BL formation as the processes of specific energy increasing and concentrating of a part of the atoms of the active plasma medium in the form of energy-structure self-organization on the base of metastable excited substance and the interchange.
The interchange is a complex of mass-energy transfer phenomena with a preferred direction [3]. Self-focusing and convergence of transport-wave fluxes, which have small loss in the metastable substance as in a active medium, may result in appearing of energy distribution inhomogeneities which should be then significantly strengthened by non-linear effects in heterogeneous dense plasma. Segregation of exited states with highest specific energy, which arise in regions of higher nonequilibrium, may results in forming of a new phase which come apart as an autonomous object a ball lightning.
All above mentioned phenomena taken separately are well known, and the task of the realization of energy-structure self-organization consists in self-consistent combining of them in single and likely multi-stage process which could go far enough, first of all, in respect of the specific energy of output phase atoms.
Erosive capillary discharge plasma
Investigations of the erosive plasma of electrical capillary discharge have confirmed the capability of supercooled erosive plasma with condensed phase to create a substance resembling the one we are looking for [4]. Many interesting properties of this plasma have been discovered, but achieved parameters were found to be insufficient for direct laboratory reproducing of the ball lightning.
With all variety of discharge modes and dischargers designs and materials, the capillary discharge allows to obtain the plasma with sufficiently large range of characteristics. Avramenko R.F. have found a discharge regime creating long and thin plasma jet with the following properties: the low temperature together with the formation enthalpy being about the total single ionization energy, effective liberation of a considerable part of the input energy on metallic targets, long life time after the disconnection from the energy source and capability to generate autonomous plasma formations when interacting with some targets, etc [5]. Further investigations [6] show that the jet has pronounced structural features, its vibrational temperature is in the order of magnitude greater than the gasokinetic one and that the interaction of the jet substance with the microwave radiation is of the threshold character [7].
Critical mode of the discharge
In papers [3,8-10] a series of peculiarities of the capillary discharge near the critical voltage value, below of which the stationary discharge is impossible, have been found. For example, at this mode occurs a drastical change of the form of the plasma jet from asymmetric capillary discharger. One more feature of the critical mode in the case of the asymmetric discharger is generation of low-frequency oscillations of the current and the voltage on the discharge which appear only when the negative potential is applied to the inner electrode, similarly to the corona discharge on the electrode of small curvature radius.
In the symmetric discharger, representing a through hole in a polymer plate, at the critical mode, the jet appears only in the negative electrode direction, see these figures.
These effects together with another ones, not mentioned here, showed that the critical mode is characterized not only by increasing of the mobility of positive carriers with respect to negative ones, but even (on some stage) by the possibility of motion of the carriers against to the external field, which is possible only after preaccumulation of the energy and formation of corresponding activity of the medium (similar phenomena are considered by Stepanov S.I. [11]). Increasing of the current part transferred by positive carriers, similarly to the cathode layer of the glow discharge, may be explained in this case by increasing of the positive particles charge, connected, in particular, with the increasing of their sizes and with decreasing on the ionization energy due to the presence of the metastable phase.
So, under effective carriers binding the transition to
the critical mode and the conductivity decreasing are due to the decreasing
of the carriers mobility and their leaving to the external area. To maintain
the conductivity new carriers should be created in the discharge together
with increasing of the charge of existing carriers. This process results
in the appearing and growth of metastable substance particles and, therefore,
is very important for the experimental ball lightning modeling.
Dynamic state of excited metastable substance
In [3] it was found that the metastable substance of the erosive discharge jet can be at a dinamic state. This state is characterized by the interchange process which represent, in this case, a complex of energy-mass transfer phenomena in the form of wave-transport fluxes with preferential direction along the jet.
For existance of the metastable phase a relatively stable spatial charges separation is necessary. In general, systems of fields preventing the charges from recombination need not necessarily be of the stationary wave character. It may be a travelling wave provided that the separated charges are frozen into the corresponding regions of the transport wave field.
In particular, for metastable substance on the base of
ionized heavy particles in electronegative mediums (gases, aerosols, liquids)
the following situation is possible. If mobilities of large charge heavy
particles (e.g. multiply charged ions) and of small particles (electrons)
are different, then, the velocity lag of the latters together with the
charge trapping lead to the charges separation which is necessary for the
metastability. Stability of this (avalanche) charge separation is directly
determined by the mobilities difference and by the effect of an external
force stimulating the metastable substance motion. The mobilities difference
may be connected with onset of oscillations in system of particles of only
one sign.
Excitation of the substance by ablation roughing of the particles
Under the interchange conditions powerful energy fluxes
act on the heavy particles surface resulting in their ionization. At the
dynamic state of the metastable substance the torn off electrons move away
from the particles, so the quasineutrality condition is not satisfied on
the particle surface, which involve them in the radiation energy exchange.
In the critical mode, when the mobility of the particles is directly related
with their charges, the most heavily ionized particles, moving faster than
the others, outrun the energy bunch that determine the conic form of the
flux. Energy transfer along the bunch motion direction under condition
of the conic form of the flux serves as energy pumping and increases ionization
degree of particles at the end of the jet. Then, the jet end detaches and
forms a new bunch with higher specific energy of the particles, etc. This
process may occur in the form of consequent detachment and disintegration
of the bunchs.
Results
The method developed by us allows to create the energy-containing
long-living autonomous objets. The best of obtained by us objects, which
can be considered as analogs of the ball lightning, have the following
characteristics: the diameter less then 1cm, the life time ~1s, the energy
density ~100J/cm3; these objets float at the atmosphere, burn
through the foil, can guide along the wall
(see Experiments)
Appearance and existence of the BL-like autonomous objects may be described by the following scheme:
References
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