plasmapy.formulary.parameters.Bohm_diffusion(T_e: Unit(‘K’), B: Unit(‘T’))

Return the Bohm diffusion coefficient.

The Bohm diffusion coefficient was conjectured to follow Bohm model of the diffusion of plasma across a magnetic field and describe the diffusion of early fusion energy machines. The rate predicted by Bohm diffusion is much higher than classical diffusion, and if there were no exceptions, magnetically confined fusion would be impractical.

\[D_B = \frac{1}{16} \frac{k_B T}{e B}\]

where \(k_B\) is the Boltzmann constant and \(e\) is the fundamental charge.

Aliases: DB_

  • T_e (Quantity) – The electron temperature.

  • B (Quantity) – The magnitude of the magnetic field in the plasma.


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



>>> import astropy.units as u
>>> T_e = 5000 * u.K
>>> B = 10 * u.T
>>> Bohm_diffusion(T_e, B)
<Quantity 0.00269292 m2 / s>
>>> T_e = 50 * u.eV
>>> B = 10 * u.T
>>> Bohm_diffusion(T_e, B)
<Quantity 0.3125 m2 / s>

  • D_B (Quantity)

  • The Bohm diffusion coefficient in meters squared per second.