The Collaborative International Dictionary of English v.0.48:

magnetic equator \magnetic equator\ n.
   An imaginary line paralleling the equator where a magnetic
   needle has no dip, the dipping needle being horizontal;
   called also aclinic line.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

aclinic line
    n 1: an imaginary line paralleling the equator where a magnetic
         needle has no dip [syn: aclinic line, magnetic equator]