Plasma parameters (plasmapy.formulary.parameters)


The plasmapy.formulary.parameters module is deprecated and will be removed in the release of v0.9.0. Please update your code to import directly from plasmapy.formulary or the specific submodule the functionality is defined in. For example,

from plasmapy.formulary import Alfven_speed

# or

from plasmapy.formulary.speeds import Alfven_speed

Functions to calculate fundamental plasma parameters.


Alfven_speed(B, density[, ion, z_mean])

Calculate the Alfvén speed.

Bohm_diffusion(T_e, B)

Return the Bohm diffusion coefficient.

Debye_length(T_e, n_e)

Calculate the characteristic decay length for electric fields,

Debye_number(T_e, n_e)

Return the number of electrons within a sphere with a radius of the Debye length.

gyrofrequency(B, particle[, signed, Z, to_hz])

Calculate the particle gyrofrequency in units of radians per second.

gyroradius(B, particle, *[, Vperp, T_i, T])

Return the particle gyroradius.

Hall_parameter(n, T, B, ion, particle[, ...])

Calculate the particle Hall parameter for a plasma.

inertial_length(n, particle)

Calculate a charged particle's inertial length.

ion_sound_speed(T_e, T_i, ion[, n_e, k, ...])

Return the ion sound speed for an electron-ion plasma.

kappa_thermal_speed(T, kappa, particle[, method])

Return the most probable speed for a particle within a Kappa distribution.

lower_hybrid_frequency(B, n_i, ion[, to_hz])

Return the lower hybrid frequency.


Calculate the magnetic energy density.


Calculate the magnetic pressure.

mass_density(density, particle[, z_ratio])

Calculate the mass density from a number density.

plasma_frequency(n, particle[, z_mean, to_hz])

Calculate the particle plasma frequency.

thermal_pressure(T, n)

Return the thermal pressure for a Maxwellian distribution.

thermal_speed(T, particle[, method, mass, ndim])

Calculate the speed of thermal motion for particles with a Maxwellian distribution.

thermal_speed_coefficients(method, ndim)

Get the thermal speed coefficient corresponding to the desired thermal speed definition.

upper_hybrid_frequency(B, n_e[, to_hz])

Return the upper hybrid frequency.


PlasmaPy provides aliases of the most common plasma functionality for user convenience. Aliases in PlasmaPy are denoted with a trailing underscore (e.g., alias_). For further details, please refer to the contributor guide’s section on aliases.

cs_(T_e, T_i, ion[, n_e, k, gamma_e, ...])

Alias to ion_sound_speed.

cwp_(n, particle)

Alias to inertial_length.

DB_(T_e, B)

Alias to Bohm_diffusion.

lambdaD_(T_e, n_e)

Alias to Debye_length.

nD_(T_e, n_e)

Alias to Debye_number.

oc_(B, particle[, signed, Z, to_hz])

Alias to gyrofrequency.


Alias to magnetic_pressure.

pth_(T, n)

Alias to thermal_pressure.

rc_(B, particle, *[, Vperp, T_i, T])

Alias to gyroradius.

rho_(density, particle[, z_ratio])

Alias to mass_density.

rhoc_(B, particle, *[, Vperp, T_i, T])

Alias to gyroradius.


Alias to magnetic_energy_density.

va_(B, density[, ion, z_mean])

Alias to Alfven_speed.

vth_(T, particle[, method, mass, ndim])

Alias to thermal_speed().

vth_kappa_(T, kappa, particle[, method])

Alias to kappa_thermal_speed.

wc_(B, particle[, signed, Z, to_hz])

Alias to gyrofrequency.

wlh_(B, n_i, ion[, to_hz])

Alias to lower_hybrid_frequency.

wp_(n, particle[, z_mean, to_hz])

Alias to plasma_frequency.

wuh_(B, n_e[, to_hz])

Alias to upper_hybrid_frequency.


Lite-functions are optimized versions of existing plasmapy functions that are intended for applications where computational efficiency matters most. Lite-functions accept numbers and NumPy arrays that are implicitly assumed to be in SI units, and do not accept Quantity objects as inputs. For further details, please refer to the contributor guide’s section on lite-functions.


Lite-functions do not include the safeguards that are included in most plasmapy.formulary functions. When using lite-functions, it is vital to double-check your implementation!

plasma_frequency_lite(n, mass, z_mean[, to_hz])

The lite-function for plasma_frequency.

thermal_speed_lite(T, mass, coeff)

The lite-function for thermal_speed.