The Debye Length

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Date: Tue, 23 Feb 1999 08:59:41 -0500
From: Burch Seymour

Debye length:

The electric field of an isolated charged particle diminishes as the square of the distance from the particle. In a plasma, however, this field is modified because the electrons are free to move into the vicinity of positive ions and away from other electrons. The field of each isolated particle is thus partially shielded by its immediate neighbors. Over a sufficiently large distance--wherein the fields of many individual charges are able to cancel each other--this shielding becomes complete. This distance, called a Debye length, is a measure of the distance over which an individual charged particle can exert an effect. Volumes greater in radius than a Debye length must be approximately neutral. The Debye length is equal to (6.9 times the square root of (T/n))centimeters, where T is the temperature of the electrons in Kelvins and n(e) is the number of electrons per cubic centimeter. For a body of particles to behave as a plasma, its dimensions must be large compared to the Debye length.

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