inertial_length

plasmapy.physics.parameters.inertial_length(n, particle='e-')

Calculate the particle inertial length. At this length, the Hall effect becomes important.

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), which defaults to electrons. If no charge state information is provided, then the particles are assumed to be singly charged.

Returns:

d – Particles inertial length in meters.

Return type:

Quantity

Raises:

• TypeError – If n not a Quantity or particle is not a string.
• UnitConversionError – If n is not in units of a number density.
• ValueError – The particle density does not have an appropriate value.

Warns:

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

Notes

The particle inertial length is also known as an particle skin depth and is given by:

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

Example

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