Plasmoid

A plasmoid is a coherent structure of plasma and magnetic fields. Plasmoids have been proposed to explain natural phenomena such as ball lightning, magnetic bubbles in the magnetosphere, and objects in cometary tails, in the solar wind, solar atmosphere, and in the heliospheric current sheet. Plasmoids produced in the laboratory include the compact toroids (similar to a vortex ring in low temperature fluid dynamics or hydrodynamics) field-reversed configurations, spheromaks, and filamentary variants in dense plasma focuses.

The word plasmoid was coined in 1956 by Winston H. Bostick (1916–1991) to mean a "plasma-magnetic entity":

Bostick researched the basic traits, and many details, of plasmoids.

A plasmoid has an internal pressure stemming from both the gas pressure of the plasma and the magnetic pressure of the field. To maintain an approximately static plasmoid radius, this pressure must be balanced by an external confining pressure. In a field-free vacuum, a plasmoid expands and dissipates rapidly.

Plasmoids have been formed in discharges with local magnetic field strengths on the order of 16,000 Tesla.

Bostick went on to apply his theory of plasmoids to astrophysics phenomena. His 1958 paper, applied plasma similarity transformations to pairs of plasmoids fired from a plasma gun (dense plasma focus device) that interact in such a way as to simulate an early model of galaxy formation.

• Bostick, W. H., "Experimental Study of Plasmoids", Electromagnetic Phenomena in Cosmical Physics, Proceedings from IAU Symposium no. 6. Edited by Bo Lehnert. International Astronomical Union. Symposium no. 6, Cambridge University Press, p. 87.

• ADS Abstract references