A plasmoid is a coherent structure of

plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...

and

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

s. Plasmoids have been proposed to explain natural phenomena such as ball lightning, magnetic bubbles in the

magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior dynam ...

, and objects in cometary tails, in the solar wind, in the solar atmosphere, and in the heliospheric current sheet. Plasmoids produced in the laboratory include field-reversed configurations, spheromaks, and in dense plasma focuses. The word ''plasmoid'' was coined in 1956 by

Winston H. Bostick Winston H. Bostick (March 5, 1916 – January 19, 1991) was an American physicist who discovered plasmoids, plasma focus, and plasma (physics), plasma vortex phenomena. He simulated cosmical astrophysics with laboratory Plasma (physics), plasma e ...

(1916-1991) to mean a "plasma-magnetic entity":

The plasma is emitted not as an amorphous blob, but in the form of a torus. We shall take the liberty of calling this toroidal structure a plasmoid, a word which means plasma-magnetic entity. The word plasmoid will be employed as a generic term for all plasma-magnetic entities.

Plasmoid characteristics

Bostick wrote:

Plasmoids appear to be plasma cylinders elongated in the direction of the magnetic field. Plasmoids possess a measurable magnetic moment, a measurable translational speed, a transverse electric field, and a measurable size. Plasmoids can interact with each other, seemingly by reflecting off one another. Their orbits can also be made to curve toward one another. Plasmoids can be made to spiral to a stop if projected into a gas at about 10⁻³ mm Hg pressure. Plasmoids can also be made to smash each other into fragments. There is some scant evidence to support the hypothesis that they undergo fission and possess spin.

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, for example, a plasmoid will rapidly expand and dissipate. Plasmoids have been formed in discharges with local magnetic field strengths on the order of 16,000 Tesla.

Cosmic applications

Bostick went on to apply his theory of plasmoids to

astrophysics Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. As one of the founders of the discipline said, Astrophysics "seeks to ascertain the nature of the h ...

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.,
What laboratory-produced plasma structures can contribute to the understanding of cosmic structures both large and small
(1986) ''IEEE Transactions on Plasma Science'' (ISSN 0093-3813), vol. PS-14, Dec. 1986, p. 703-717.

Footnotes

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References

* 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

Plasmoid characteristics

Cosmic applications

See also

Footnotes

References

See also