inertial_length

plasmapy.physics.parameters.inertial_length(n: Unit("1 / m3"), particle: plasmapy.atomic.particle_class.Particle)

Calculate a charged particle’s inertial length.

Parameters
  • n (Quantity) – Particle number density in units convertible to m ** -3.

  • particle (str, optional) – Representation of the particle species (e.g., ‘p+’ for protons, ‘D+’ for deuterium, or ‘He-4 +1’ for singly ionized helium-4).

Returns

d – The particle’s inertial length in meters.

Return type

Quantity

Raises
Warns

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

Notes

The inertial length of a particle of species \(s\) is given by

\[d = \frac{c}{\omega_{ps}}\]

The inertial length is the characteristic length scale for a particle to be accelerated in a plasma. The Hall effect becomes important on length scales shorter than the ion inertial length.

The inertial length is also known as the skin depth.

Example

>>> from astropy import units as u
>>> inertial_length(5 * u.m ** -3, 'He+')
<Quantity 2.02985802e+08 m>
>>> inertial_length(5 * u.m ** -3, 'e-')
<Quantity 2376534.75601976 m>