Answer
The magnetic force depends on the particle’s motion, and is not uniquely determined at a point in space.
Work Step by Step
The magnetic force $\vec{F}=q\vec{v}\times \vec{B}$.
The direction depends on both the particle’s velocity $\vec{v}$ and the magnetic field $\vec{B}$, so we cannot define the force’s direction solely by knowing the direction of the magnetic field $\vec{B}$.
