Here is an excerpt from a book: Notice also how the charged particle is captured by the magnetic field, just drifting along the field direction. In my book, the field direction is in the y-direction, but the in addition to the particle having an initial y velocity, it had an initial z velocity as well. So it seems to me that the particle is drifting not in the direction of the field, but traveling in yz space. Am I understanding this right? Thank you.