Ball Lightning and Plasma Physics

Finding plasma in nature is a little tricky, because it has the tendency to absolutely obliterate anything it touches, but luckily thermodynamics will usually sort this out by cooling the plasma matter down so quickly that it can't do too much damage. The most readily familiar phenomenon that involves the creation of plasma is of course lightning, whose charge carriers travel in a "lightning channel" consisting of atmospheric plasma, filaments of ionized air, the organization of which determines the shape of the lightning. In lightning physics, the components of lightning are streamers, caused by nonlinear plasma ionization waves and manifesting in "finger-shaped" structures probing for further propagation of the main body of the lightning; leaders, characterized mostly by high plasma temperature and low resistance, manifesting in the large and fast-moving main body of the lightning; and the return stroke channel, which runs back the channel once the lightning discharges on a grounding structure, neutralizing the channel as it travels upward. The return stroke brings the entire channel to a very high temperature (30k K), and thus to a local thermodynamic equilibrium. The other two components are nonequilibrium plasma, and thus have a very short lifetime either way. Within a nonequilibrium plasma, the electron temperatures are usually much higher than that of neutral particles, collision rates between charged and neutral particles are high, and ionization is rare. From these, the ability to shield short-range interaction between individual particles, quasi-neutrality and collective response to long range electromagnetic forces is derived. The categories of equilibrium and non-equilibrium are admittedly somewhat squishy. There is, also a different kind of lightning, which behaves differently, and thus will have a different composition in terms of plasma.

Ball Lightning is one of those freak-of-nature phenomena. Rarely occurring, and even more rarely documented. Because of the geometry of ball lightning, the energy is much more localized. Intuitively, these phenomena demonstrate a high energy density, which translate into very high temperatures. Energy density can be determined using the phenomenon's effect on its surroundings, using known capacities, potentials or other convenient quantity for an experiment. Because of the geometry, ball lightning should be expected to have something akin to surface tension, which might interact with other electrodynamic forces.

Artificial creation of ball lightning uses capacitive energy storage, high-voltage chargers, a commutation unit and an electric-discharge spheretron. Direct data about ball lightning is usually taken through optical means through a filter medium. A proposed method of finding the diameter, for example, has the ball lightning pass through a filter just thick enough, so only a dark spherical formation is observable on it. Supposedly, the diameter of this formation is approximate to that of the ball lightning's core, motivated by parallels between ball lightning and small black holes.

Ball lightning consists of a core (surplus negative charge/electrons) and an external spherical shell (surplus positive charge/nuclei or heavy particles). The ball lightning is characterized by a strong radial electric field between the two components, which pushes them apart with at least past the Debye length, the ball lightning rotates around some axis. The electric field then has a radial, ambipolar and external components. The ambipolar field is that between the core and the shell, created by the different rotations of the core and shell. The ball lightning then gains a poloidal magnetic field. The rotational moment of the plasma stems from the plasma vortex during its generation. This happens through a process called "magnetic dynamo".

Beyond the shell is a halo, basically consisting of an electric field built between the shell, and the surrounding atmosphere. It's weaker than that between core and shell. The measurable electric field of the ball lightning is a vector sum of its components. During the generation process, the intensity of the electric field changes, though it'll turn out with a very high intensity regardless, the radial component easily exceeding the limit beyond which electrical breakdown occurs. Between core and shell, electrical breakdown is staved off by the induced magnetic field, since it confines the core's electrons from traveling outward. Stability of ball lightning is determined by the potency of the magnetic field within, as it significantly suppresses recombination of the components. The magnetic field itself is created by a closed circular current of relativistic particles from the external spherical layer.

Because of the energy scales at which ball lightning interacts with matter, it can be assumed that doing so will generate neutrinos. The process of ball lightning passing through matter could then be related to the process underlying the air showers that occur when high-energy particles impact the atmosphere. Superficial differences include the medium density being much higher in glass than atmosphere, and the energy of primary particles being lower than those impacting the atmosphere. The magnetic field of the ball lightning is also much higher than that of the earth. It's also notable that the protons in the ball lightning are polarized as they pass through the filter. One would expect the filter to absorb the magnetic field at sufficient thickness, though this doesn't seem to be the case in experiments. The observations suggest neutrino generation. The direction of motion in the ball lightning can be shown by suspending a metal plate on a single point. On contact with dark ball lightning, the sheet will display oscillations, which means that particles impart momentum. Probing the signals reveals variable particle charges. The usual contraptions used for particle detectors can be used to detect muons and neutrinos beyond an absorber.

Stability of the ball lightning happens at balanced centrifugal force and electrical force. The equation. This is most relevant for the most massive particle, as that maximizes the centrifugal force. There have been ball lightnings observed with a radius of 12.5 cm and an electric field strength of E = 2.3e4 V/cm, which would imply a proton energy that is typical for cyclotron-sources. It's below the threshold to trigger cascades though. Protons will somehow need to gain enough energy to generate pions when entering a dense medium. This might be analogous to the cosmic ray acceleration when entering clouds of gas in medium magnetic fields, or perhaps expanding sunspots. The latter one shares the magnetic field flux, which means that the acceleration of charged particles is time-dependent through the magnetic field. The magnetic fields flux is dictated by an electric field, accelerating charged particles up to relativistic energies. Determining the proton energy can be done using the cyclotron mechanism and a magnetic flux potential adhering to Faraday's law.

Once the proton energy is elevated sufficiently to generate pions, the cascades are motivated. The cause of excess elementary particles are thus a product of generated primary particles. When protons with energies E > 140 MeV collide with a the absorbing filter particles, diverse kinds of pions are generated, which then decay as should be familiar from particle physics. The neutral pion decays into two photons, which in turn trigger electron/positron showers in the Coulomb field of the filter nuclei. The charged pions decay into a muon of the same charge, and the complementary neutrino, which in turn decay into electron/positron and neutrinos for muons and electrons. Assuming that the muons retain the original motion vector as their parent particles, and that the muon decay happens behind the filter, interactions between charged particles and the air particles behind the filter ionizes the atoms. As the poloidal magnetic field penetrates into the filter, the induction of the magnetic field changes with time, and thus induces an (azimuthal) electric field vortex. This in turn facilitates charge separation in the region behind the filter, which recreates the shell and core of the ball lightning by charged particle drift.. The ball lightning with excess rotational momentum appear as a result of the inequality of the charged particle fluxes behind the filter. When the forces are balanced again, the ball lightning is fully reformed. Dark ball lightning is associated with low charge.