An electric field accelerates {HEAD ~ ions} and electrons in {TAIL ~ directions} parallel to the electric field 
in
An electric field accelerates { HEAD ~ ions } and electrons in { TAIL ~ directions } parallel to the electric field
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH