# Collisions (plasmapy.formulary.collisions)

The collisions subpackage contains commonly used collisional formulae from plasma science.

## Sub-Packages & Modules

 coulomb This module contains functionality for calculating Coulomb parameters for different configurations. dimensionless Module of dimensionless parameters related to collisions. frequencies Frequency parameters related to collisions. lengths Module of length parameters related to collisions. misc Module of miscellaneous parameters related to collisions.

## Classes

 Compute collision frequencies between two slowly flowing Maxwellian populations. Compute collision frequencies between test particles (labeled 'a') and field particles (labeled 'b').

## Functions

 collision_frequency(T, n, species[, z_mean, ...]) Collision frequency of particles in a plasma. Coulomb_cross_section(impact_param) Cross-section for a large angle Coulomb collision. Coulomb_logarithm(T, n_e, species[, z_mean, ...]) Compute the Coulomb logarithm. coupling_parameter(T, n_e, species[, ...]) Ratio of the Coulomb energy to the kinetic (usually thermal) energy. Average momentum relaxation rate for a slowly flowing Maxwellian distribution of electrons. fundamental_ion_collision_freq(T_i, n_i, ion) Average momentum relaxation rate for a slowly flowing Maxwellian distribution of ions. impact_parameter(T, n_e, species[, z_mean, ...]) Impact parameters for classical and quantum Coulomb collision. impact_parameter_perp(T, species[, V]) Distance of the closest approach for a 90° Coulomb collision. Knudsen_number(characteristic_length, T, ...) Knudsen number (dimensionless). mean_free_path(T, n_e, species[, z_mean, V, ...]) Collisional mean free path (m). mobility(T, n_e, species[, z_mean, V, method]) Return the electrical mobility. Spitzer_resistivity(T, n, species[, z_mean, ...]) Spitzer resistivity of a plasma.

Examples