Debye_length

plasmapy.formulary.lengths.Debye_length(T_e: Unit('K'), n_e: Unit('1 / m3'))

Calculate the characteristic decay length for electric fields due to charge screening.

Aliases: lambdaD_

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:

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

\[λ_D = \sqrt{\frac{ε_0 k_B T_e}{n_e e^2}}\]

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

Examples

>>> import astropy.units as u
>>> Debye_length(5e6*u.K, 5e15*u.m**-3)
<Quantity 0.002182... m>