The Debye length is the scale over which mobile charge carriers screen out electric fields in plasmas and other conductors.
Debye length in a plasma
In SI units, it is
where
λD is the Debye length,
ε0 is the permittivity of free space,
k is Boltzmann's constant,
Te and Ti are the temperatures of the electrons and ions, respectively,
ne is the density of electrons,
qe is the charge on an electron,
Z is the ionization state of the ions,
The ion term is often dropped, giving
although this is only valid when the electrons are much colder than the ions.
Debye length in an Electrolyte
In an electrolyte, the Debye length is given by
.
Reference
Equation for Debye length copied from Goldston & Rutherford's Introduction to Plasma Physics, Institute of Physics Publishing, Philadelphia: 1997, p. 15)