The Senftleben–Beenakker effect is the dependence on a magnetic or electric field of transport properties (such as viscosity and heat conductivity) of polyatomic gases.
The effect is caused by the precession of the (magnetic or electric) dipole of the gas molecules between collisions.
The resulting rotation of the molecule averages out the nonspherical part of the collision cross-section, if the field is large enough that the precession time is short compared to the time between collisions (this requires a very dilute gas).
A key difference is that the gas molecules are neutral, unlike the electrons, so the magnetic field exerts no Lorentz force.
[2] The Senftleben–Beenakker effect owes its name to the physicists Hermann Senftleben (Münster University, Germany) and Jan Beenakker (Leiden University, The Netherlands), who discovered it, respectively, for paramagnetic gases [3] (such as NO and O2) and diamagnetic gases [4] (such as N2 and CO).