An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A plasma in which the → mean free path of the → charged particles between two → collisions is much smaller than the size of the system containing the plasma.

→ collisional; → plasma.

Plasma in which magnetic field lines forming closed surfaces confine the plasma.

Confined, p;p. of → confine; → plasma.

A plasma containing a magnetic field which is strong enough to change the path of charged particles. It can be a → collisional plasma or → noncollisional plasma.

→ magnetized; → plasma.

A plasma in which the → mean free path of the charged particles between two collisions is much larger than the size of the system containing the plasma.

→ non-; → collisional; → plasma.

The plasma filling space before the → recombination epoch that mainly consisted of → cosmic microwave background radiation photons, electrons, protons, and → light elements.

→ photon; → baryon; → plasma.

In physics, a gas in which an important fraction of the atoms is ionized, so that the electrons and ions are separately free. Plasma, often described as the fourth state of matter, occurs at extremely high temperatures, as in the interiors of stars, in fusion reactors, and in the interstellar medium ionized by hot stars.

From L.L. plasma, from Gk. plasma "something molded or formed," from plassein "to mold," originally "to spread thin."

Plâsmâ, loan from Fr.

In plasma physics, a dimensionless quantity which is the ratio of the plasma thermal pressure to the magnetic pressure: β = nkT/(B²/2μ₀). When β is much smaller than 1, like in the → solar corona, the magnetic forces dominate over the plasma forces.

→ plasma; β, Gk. letter of alphabet.

An alternative cosmology, initially conceived by Hannes Alfvén in the 1960s, that attempts to explain the development of the visible Universe through the interaction of electromagnetic forces on astrophysical plasma. Like the steady state model, plasma cosmology hypothesizes an evolving Universe without beginning or end.

→ plasma; → cosmology.

The natural frequency at which internal oscillations of a plasma occur. The plasma frequency is proportional to the square root of the electron density. → plasma oscillation.

→ plasma; → frequency.

(Geophysics): A layer of plasma located on the night-side of Earth, inside the magnetosphere and along its boundary. Under the action of electromagnetic forces, plasma contained in the mantle drifts equator-ward, along the tail axis.

→ plasma; → mantle.

The oscillatory motion of electrons in a neutral plasma around their equilibrium position while the ions remain at rest. When electrons are displaced by any kind of perturbation with respect to ions, a pair of positive and negative charged regions is formed. The Coulomb force accelerates back the displaced electrons, which get kinetic energy. The electrons overshoot their original positions by the same amount as their first displacement.

→ plasma; → oscillation.

The study of the physical properties of the various forms of plasmas and their processing.

→ plasma; → physics.

The ionized component of a comet's tail, driven nearly straight away from the Sun by the solar wind. Also called ion tail and gas tail.

→ plasma; → tail.

The sharp outer boundary of the plasmasphere, at which the plasma density decreases by a factor of 100 or more.

→ plasma + pause "break, cessation, stop," from M.Fr. pause, from L. pausa "a halt, stop, cessation," from Gk. pausis "stopping, ceasing," from pauein "to stop, to cause to cease."

→ plasma + marz "frontier, border, boundary," from Mid.Pers. marz "boundary;" Av. marəza- "border, district," marəz- "to rub, wipe;" Mod.Pers. parmâs "contact, touching" (→ contact), mâl-, mâlidan "to rub;" PIE base *merg- "boundary, border;" cf. L. margo "edge" (Fr. marge "margin"); P.Gmc. *marko; Ger. Mark; E. mark, margin.

In the magnetosphere, a region of relatively cool (low energy) and dense plasma that may be considered an outer extension of the ionosphere with which it is coupled. Like the ionosphere, the plasmasphere tends to co-rotate with the Earth.

→ plasma + → sphere.

A plasma characterized by a → turbulent flow regime.

→ turbulent; → plasma.