Maxwellian_speed_3D¶

plasmapy.physics.distribution.Maxwellian_speed_3D(vx, vy, vz, T, particle='e', Vx_drift=0, Vy_drift=0, Vz_drift=0, vTh=nan, units='units')¶

Return the probability of finding a particle with speed components vx, vy, and vz`in m/s in an equilibrium plasma of temperature `T which follows the 3D Maxwellian distribution function. This function assumes Cartesian coordinates.

Parameters:	vx (Quantity) – The speed in x-direction units convertible to m/s. vy (Quantity) – The speed in y-direction units convertible to m/s. vz (Quantity) – The speed in z-direction units convertible to m/s. T (Quantity) – The temperature, preferably in Kelvin. particle (str, optional) – Representation of the particle species(e.g., ‘p’ for protons, ‘D+’ for deuterium, or ‘He-4 +1’ for \(He_4^{+1}\) (singly ionized helium-4), which defaults to electrons. Vx_drift (Quantity) – The drift speed in x-direction units convertible to m/s. Vy_drift (Quantity) – The drift speed in y-direction units convertible to m/s. Vz_drift (Quantity) – The drift speed in z-direction units convertible to m/s. vTh (Quantity, optional) – Thermal velocity (most probable) in m/s. This is used for optimization purposes to avoid re-calculating vTh, for example when integrating over velocity-space. units (str, optional) – Selects whether to run function with units and unit checks (when equal to “units”) or to run as unitless (when equal to “unitless”). The unitless version is substantially faster for intensive computations.
Returns:	f – Probability in speed^-1, normalized so that: \(\iiint_{0}^{\infty} f(\vec{v}) d\vec{v} = 1\).
Return type:	Quantity
Raises:	`TypeError` – A parameter argument is not a `Quantity` and cannot be converted into a `Quantity`. `UnitConversionError` – If the parameters is not in appropriate units. `ValueError` – If the temperature is negative, or the particle mass or charge state cannot be found.

Notes

In one dimension, the Maxwellian speed distribution function describing the distribution of particles with speed \(v\) in a plasma with temperature \(T\) is given by:

\[f = 4 \pi \vec{v}^2 (\pi * v_Th^2)^{-3/2} \exp(-(\vec{v} - \vec{V_{drift}})^2 / v_Th^2)\]

where \(v_Th = \sqrt(2 k_B T / m)\) is the thermal speed.