Speed Plasma Parameters (plasmapy.formulary.speeds)

Functions to calculate fundamental plasma speed parameters.


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

Calculate the Alfvén speed.

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.

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.


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.

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.


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!

thermal_speed_lite(T, mass, coeff)

The lite-function for thermal_speed.