In this video here are those pink green the magnetic field lines? If so where does the proton come from? If I'm not mistaken a charged particle in motion will only be influenced by the magnetic field if its not moving parallel to the magnetic field lines but in this video the proton appears to be moving in the direction of the magnetic field lines its only the centripetal motion thats perpendicular to the green lines. Does that mean the proton flies into the magnetic field then gets stuck in that circular trajectory? If so whats causing it to move in the direction of the magnetic field lines? For example in this diagram http://img59.imageshack.us/img59/4016/mfield114.gif [Broken] Would that black arrow be the direction that the charged particle comes in or are the pink arrows the direction of the particles velocity before it entered the magnetic field?