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The plasma parameter is a dimensionless number, denoted by capital Lambda, Λ, which measures the average number of electrons contained within a Debye sphere (a sphere of radius the Debye length) in a plasma (but note that the word parameter is usually used in plasma physics to refer to bulk plasma properties in general: see plasma parameters). It is defined as:
Additional recommended knowledge
Often the factor of 4π / 3 is dropped. When the Debye length is given by , the plasma parameter is given by:
The natural logarithm of the plasma parameter, lnΛ, is the Coulomb Logarithm.
The plasma approximation
One of the criteria which determines whether a collection of charged particles can rigorously be termed a plasma is that Λ>>1. When this is the case, collective electrostatic interactions dominate over binary collisions, and the plasma particles can be treated as if they only interact with a smooth background field, rather than through pairwise interactions (collisions) .
Plasma properties and Λ
The magnitude of Λ can be summarised below :
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Plasma_parameter". A list of authors is available in Wikipedia.|