(Or dip equator, magnetic equator.) The line through those points on the earth's surface at which the magnetic inclination is zero.
The aclinic line is a particular case of an isoclinic line. In South America the aclinic line lies at about 15°S latitude, while from central Africa to about Indochina it coincides approximately with the parallel of 10°N latitude.
Compare agonic line, geomagnetic equator.
