EUROPEAN PHYSICAL SOCIETY
10th General Conference "Trends in Physics"
Sevilla 9-13, 1996
Abstracts of Contributed Papers, p 10
Arne Bergström
Scientor Research & Development
Essingekroken 9, S-112 65 Stockholm, Sweden
phone +46 8 695 0600 fax +46 8 695 0312
e-mail arne.bergstrom@scientor.se
Observations of ball
lightning seem to indicate that this enigmatic phenomenon could occasionally
represent storage of very large energies (up to 10 MJ) in volumes of air
of the order of liters at essentially normal density (since ball lightnings
are reported to have essentially neutral buoyancy).
Assuming for the sake
of argument that at least some of these observations are accurate, this
raises the following two intriguing questions:
i) in what form, if any, could so large energies be stored in air, and
ii) what mechanism, if any, could account for the surprisingly long life-time (of the order of 10 sec) of these objects.
The answer to question
i) must exclude energy stored in the form of ionization, combustible
gas, and other forms of chemical energy, since the energies involved would
then at most be of the order of tens of eV per atom, wheras the energies
quoted above correspond to the order of keV per atom.
The answer to question
ii) must be consistent with the virial theorem, d2J/dt2
= W, which is a general relationship connecting the radial moment of inertia
J for a dynamic system to a total W of its kinetic, potential and electromagnetic
energies. Unless some, so far unknown, form of attraction would be present
in ball lightning, the quantity W is positive and the virial theorem then
seems to prescribe an accelerated expansion of the system.
The present communication
investigates the possibility that the answer to question i) is charge
separation in ordinary air caused by, e g, a lightning stroke or atmospheric
electric fields. It is well known that even minute charge displacements
from quasi-neutrality can produce very large restoring forces, and can
thus provide a form of storage for large quantities of energy. The paper
studies the dynamics of violent such transient deviations from charge neutrality,
and specifically the possibility of long-lived, spherically-symmetric,
radially-oscillating such deviations, the spherical symmetry being of special
interest since decay by electromagnetic radiation would then (ideally)
not be allowed. Space-time separable, spherically symmetric solutions to
the nonlinear electrodynamic equations (Maxwell's equations plus conservation
of charge, mass/energy and momentum) are found
in exact analytical form with electric field
E(r,t) = (C(t)/r)n r -2.
These solutions either (for n < 0) describe a homogeneous expansion,
or (for n > 0) stationary, radial oscillations (in which case C(t) is
a common cycloid).
Interestingly
enough, these cycloid solutions - which occur for sufficiently steep charge
distributions - are also an answer to question ii). For such radial
oscillations with cycloid time-dependence we have, due to recurring vertical
cusps, that d2J/dt2 > 0 for all times t even though
the system is not ever-expanding. Hence this type of electrodynamic self-confinement
is not excluded (but actually supported) by the virial theorem, and may
be an interesting, potential alternative to magnetic confinement for controlled
fusion.
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