Debye_length

plasmapy.physics.parameters.Debye_length(T_e, n_e)

Calculate the characteristic decay length for electric fields,

due to charge screening.

Parameters:

• T_e (Quantity) – Electron temperature
• n_e (Quantity) – Electron number density

Returns:

lambda_D – The Debye length in meters

Return type:

Quantity

Raises:

• TypeError – If either argument is not a Quantity
• UnitConversionError – If either argument is in incorrect units
• ValueError – If either argument contains invalid values

Warns:

~astropy.units.UnitsWarning – If units are not provided, SI units are assumed

Notes

The Debye length is the exponential scale length for charge screening and is given by

\[\lambda_D = \sqrt{\frac{\epsilon_0 k_b T_e}{n_e e^2}}\]

for an electron plasma with nearly stationary ions.

The electrical potential will drop by a factor of 1/e every Debye length.

Plasmas will generally be quasineutral on length scales significantly larger than the Debye length.

See also

Debye_number()

Example

>>> from astropy import units as u
>>> Debye_length(5e6*u.K, 5e15*u.m**-3)
<Quantity 0.00218226 m>