A magnetic field at the surface redirects {HEAD ~ ions} and electrons based on {TAIL ~ their velocity} and charge 
based on
A magnetic field at the surface redirects { HEAD ~ ions } and electrons based on { TAIL ~ their velocity } and charge
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH