Type:		Journal, Article
Title:		Ball lightning as a magnetostatic spherical force-free field plasmoid
Author(s):		Tsui, K. H.
Date:		2003/07/10
Abstract:		Ball lightning is regarded as a magnetostatic spherical force-free field plasmoid. The current carried by the conducting plasma is everywhere parallel to the magnetic field with the magnetic force being zero everywhere in the plasmoid. The plasma pressure is balanced by the surrounding atmospheric pressure. Although the magnetic field does not take part in pressure balance to determine the plasma equilibrium, it is responsible for confining the plasma by guiding the charged particles along the field lines. Such a configuration is the minimum energy state under the constraint of magnetic helicity conservation. Under the magnetic helicity constraint, the force-free magnetic field in a resistive glow plasmoid has to decay to a likewise force-free configuration. This inhibits the total magnetic field to be dissipated exponentially in one time constant, and restricts the overall magnetic decay to a path with a sequence of adiabatic small step force-free decays where one state differs very slightly to the neighboring state. Each small step magnetic decay is governed by a time constant which could add up to a total lifetime of many seconds.
Journal (full):		Physics of Plasmas
Volume:		10
Start Page:		4112
Link:		http://pop.aip.org/resource/1/phpaen/v10/i10/p4112_s1