Magnetic Force
The Magnetic Force node is only available when Newtonian or Newtonian, first order is selected as the Formulation on the Settings window for The Particle Tracing for Fluid Flow Interface.
Use the Magnetic Force node to exert a magnetic force to the particles. A magnetic force alone does no work on the particles, so in the absence of any other external forces, the particle retains its original energy. The force is specified via a magnetic flux density.
The settings for this feature node are the same as for the Magnetic Force node described for The Charged Particle Tracing Interface.
Electric and Magnetic Forces in the theory section.