Laboratory-Produced Ball Lightning
So apparently ball lightning can be produced in a lab, if this [doi:10.1017/S0022377815000197] paper can be believed. I'm not qualified to check its veracity, so I'll have to settle for trying to understand what they did. Ball lightning is generated in a plasmic vortex, though the energy in the generation region is very different from that of the ball lightning. The axial and rotational components of the ball lightning determine its stability. The paper in question could be viewed as a culmination of experiments aimed at producing ball lightning in the Prometheus series installations. This also requires me understanding some electrical engineering, which I am very poorly equipped for. Apparently the approach is to build a mechanism to generate a a high current electrical discharge for intense fluxes of fast ions.
The first energy storage holds 11.25 kJ with charging voltage 15 kV and 1.5 C. The voltage pulse duration is meant to be 500 microseconds. The second main energy storage has a capacity of 25 kV, measurements were 18.75 kJ, with the same stored charge as in the first energy storage. This way, two ball lightnings were meant to be directed toward one another. Alternatively, generation of dipole-ball lightning is also meant to be possible. This setup opens four methods of ball lightning productions, based on the spheretron implementations.
While the spheretron is active, it generates a longitudinal magnetic field, creating a vortex electric field inside the inductor. The commutation of the spheretron is driven by high-current thyristors (?) steered with a control unit. This part doesn't work by itself. The physics is grounded in energy conversion. Commutation of the spheretron is effected by a discharges with a field distortion, initiated by a starter unit on the base of a high-voltage thyratron. The plasma luminosity reflection is shielded against with optical isolators/absorbers, so that the an optical signal can be taken for measurement. There is a typical set of diagnostic methods typical for the the high-powered pulse electronics. The measured quantities are the spheretron's voltage and current, the ball-lightning potential, and the current in the circuit of the collector during the collapse of the ball lightning. The ball-lightning potential is measured using a probe with a divider.
During the experiment, microwave radiation with wavelengths between 0.8cm and 1.6cm could be observed. When the ball lightning passes through absorbing filters, Bremsstrahlung was registered. This should be true for all solid body partially or fully absorbing charged particles flows. The rotational energy can be measured through an opening of the cylindrical plexiglass chamber. The induction magnetometer of 0.94m in diameter was used in the experiments, and installed outside the chamber.
Because of the nature of the instruments, and ball-lightning one should expect a lot of electromagnetic noise/disturbances. An attempt was made to counteract it, by taking all measurements at the same time, and gathering all ground connections. The ball lightning's passage from the spheretron to the lab's ceiling is accompanied by a high-intensity electrical soliton, leading to a contortion of images on the recording video camera, even at the maximum possible distance from the spheretron (4.5m).
The placement of the probe allows the assumption of the ball lightning as a system of electrical charges, and, with a ball lightning of approximately 25 cm in diameter after 500 ns and 2.5-2.7m from the ceiling, allows for the calculation of the ball lightning velocity in the primary region between spheretron and ceiling (5*10^8 cm/s).
Assuming an ion charge Z = 1 (lower bound), the axial component of the particle energy within the ball lightning equals 100 keV, judging by this (vertical) speed. The voltage applied to the electrodes was 15 kV, and the discharge was performed at atmospheric pressure, which result from the intense microwave radiation at charge separation. The best optical observation is obtained against the background of an intensive luminosity of plasma through a blue filter, if looking at an obstacle obscuring the ball lightning. This way, the optical signal does not overwhelm the sensors. In the experiment, the laboratory ceiling was used as such an object, but a grounded conductor, or an absorbing filter were also featured in variations.
The spheretron has a vertical deviation, which leads to the spreading of the ball lightning along the spheretron axis, but otherwise the position of the spheretron is not especially important (observation was made by orienting the spheretron downward and measuring the ceiling penetration, post deflection on floor / more deliberate installation). The thermal component in the generation zone of the ball lightning seems irrelevant for the resulting velocity vector.
The luminosity and diameter of the ball lightning could be modulated through the charge in the capacitive energy storage, though the charge was only partially transferred into the ball lightning due to the high inductance of the capacitors.
Data from the probe was collected during the collapse of the ball lightning. After iterations of the experiments, the spheretron-setup will display traces of plasma, which hints at the generation of a rotating plasma (plasmic vortex), which can be assumed to be fundamental for ball lightning generation. During the ball lightning lifetime, hot plasmoids and clusters are also emitted away from the area of generation. Charge that is "on the way to accumulation" can be grounded out prematurely, decreasing the size of the ball lightning. As every other lightning, the ball lightning will also seek to ground itself out after generation, even if that counteracts its initial velocity vector. This is also assumed to be true for the natural case. At this point, the paper likens ball lightning to a model for the formation of celestial bodies through vortices in uniform matter, due to the ball lightning's ideal sphericality, apparently unique to stars.
The short lifetime is attributed to the high axial velocity component causing it to quickly move through the lab and ground itself out in the ceiling. This velocity could technically be reduced through collision with particles in the air and neutral atoms. In nature, this initial vector can be effectively neutralized, so that the ball lightning moves only through wind effects. Unfortunately, introducing media with higher density doesn't so much slow down the ball lightning, as it absorbs its energy (read: luminosity) and reduce its lifetime. This is a result of the ball lightning tunneling, later used for determining the internal energy of the ball lightning via the black ball lightning "halo". Slowing down the ball lightning using electrical fields were also unsuccessful, even using fields of similar energy voltage scales. The electrostatic interaction between ball lightning elements are not balanced by the centripetal acceleration, but doing so could stabilize the ball lightning.
The second Prometheus experiment was created with higher rates of energy transfer from the initial energy storage to the ball lightning. For this, the energy storage is split into four modules and has a higher peak current and pulse duration. The charge and energy determines the ball lightning diameter. In the destruction of ball lightning at a collector can be observed that ball lightning is likely not a spherical layer of light radiation. The characteristic waveforms in voltages and currents in the spheretron, the probe and from the Bremsstrahlung are all heavily damped oscillations. It's superficially intuitive that the peak values are only reached in the initial pulse amplitude. It follows that the ball lightning must already be present at the initial pulse amplitude. The charge that arrives at the spheretron turns out about 4 times higher than the charging voltage of the energy storage, so what's actually measured is likely heavily influence by the ball lightning's very strong internal electric field. While the voltage drops, the ball lightning can be treated as part of the electric circuit then, with an assumed homogeneous voltage distribution. Taking the observed values of 230 kV total charge and 10 cm radius, the energy density should be sufficient for ionizing neutral atoms in the air via the strong electric field and for the electric air breakdown typical for lightning phenomena. The halo outside the ball lightning is created by the interaction of charged particle fluxes from ball lightning with the surrounding air. This is analogous to a charged particle in an accelerator. The fields themselves are a result of the charge separation within the plasma into the ball lightning kernel and surrounding shell. Specifically, the fields is generated during the formation of its electric domains, which are quasi-neutral zones that form plasma-subsystems, consisting of a region/layer with a surplus negative charge and a region/layer with a surplus positive charge. The distance between these regions needs to exceed the Debye screening length. This still qualifies some very small lengths, which in themselves will be enough for the generation of very strong electric fields. The ball lightning's electric field has a radial and ambipolar component. This quasi-neutrality also holds true on the macro-scale, as well as for the ball lightning as a whole. This has been confirmed through collecting ball lightning on a charged sheet of metal and observing no change of charge after absorption.
The rotational component of the ion energy can be measured in a cylindrical plexiglass chamber with an opening on one side, where the metal foil of variable thickness is placed for the particles to pass through. The maximum thickness gives the rotational energy component. Upon interaction, small holes appear in the foil, perhaps created by ions or other high-energy clusters. Either way, by the maximum thickness of the foil, a maximum energy of slightly beyond 1MeV is estimated. Small dents have been observed in the foil, so there are likely high-energy clusters in the external spherical layer. The velocity of the external spherical layer is about 10^9 cm/s, which translates to a rotation period of 6.3 * 10^-8 s. This implies that the inside the ball lightning consists of a circular current of relativistic particles. This current creates and maintains the poloidal magnetic field of the ball lightning, qualifying it as a magnetic dynamo.
It's not immediately clear, why momentary plasma recombination does not occur in a ball lightning. The luminosity intensity of the peripheral parts exceeds that of the center, which is a typical structure for microball lightnings. The radial distribution of luminosity is experiences a peak at about the half-way point, before collapsing. This is due to the peripheral part containing more ions than electrons, while the central part has more electrons than ions. The ball lightning consists of the kernel with surplus negative charge and external spherical layer with surplus positive charge, which means it can be viewed as a spherical electric domain. From the measurements, the inner part of the ball lightning has a strong radial electric field, with the intensity distribution following the poisson-equation.
There are ball lightnings with dipole characteristics in nature. These consist of two spherical areas at a distance, each with a surplus charge. In this case, both spheres rotate around its own axis, and around the center of mass of the system. For these, the force of the Coulomb interaction between the areas is balanced by the force caused by the centripetal acceleration.
The ball lightning obtains rotational, electric and magnetic moments at the origin of a plasma vortex. The ambipolar electric field between the kernal and external spherical layer is created through the fact that the external spherical layer causes the rotation of the kernel through electrostatic interaction between the elements with surplus charges. The rotation speed is sub-relativistic, and creating a poloidal magnetic field in space. This is in line with the Maxwell equations applied to the poloidal magnetic field (and the azimuthal current). The radial and ambipolar components of the electric field and induced electric field are caused by temporal changes of the poloidal magnetic field at the stage of generation of ball lightning. The time-varying magnetic field is connected with the vortex electric field.
Ball lightning is functionally a charged capacitor of a spherical shape with own strong electric and magnetic fields rotating in the air. The Poynting vector is nonzero, so its lines become concentric circles in planes that are perpendicular to the rotation axis of a ball lightning. Inside the ball lightning, the circulation of energy in electromagnetic field is continuous. The lines of the magnetic field inside the ball lightning are distributed between the kernel and external spherical layer. The kernel of the ball lightning is located in the area of minimum values of the magnetic field induction increasing in the radial direction. The charged particles of the kernel can't move in the radial direction. It's not impossible for an intermediate, quasi-neutral layer between the elements of the electric domains to exist to keep the plasma from self-eliminating. In this case, ball lightning would have the same structure as a radiating star. Continuous existence of ball lightning is predicated on
1. A kernel in the area with the minimum of induction of the poloidal magnetic field creating a circular current in the external spherical layer and the inability of charged particles to move toward increasing the magnetic field induction.
2. The excess charge in the kernel or external spherical layer reducing the possibility of electron capture, rendering recombination improbable.
3. Inequality of charges significantly reducing the losses of charged plasma due to bremsstrahlung.
4. The resultant of all forces is zero in the equatorial plane.
5. A reaction of nuclear fusion is possible due to the strong fields in the ball lightning and the presence of deuterium in atmospherical water vapor.
At the point of generation, the ball lightning will already need to have kinetic, electromagnetic and thermal energy due to energy conservation and thermodynamics. The kinetic energy consists of translational and rotational components. The electromagnetic energy consists of electric and magnetic field-energies.
During its lifetime, ball lightning radiates energy in the optical and bremsstrahlung spectral ranges. There is also an intense cyclotron radiation. Due to the low transmission efficiency from the Prometheus installation into the ball lightning, the lifetime of the ball lightning is fairly short. Better efficiency is likely best found in a reduction of discharge duration of the energy supply, until it's close to the formation time of the ball lightning. This timescale can be obtained through semiconductor plasma physics for a triple time of Maxwellian relaxation of the sphace charge
