Agonic

There are two lines on the earth's surface which have been called agonic lines, upon which there is no declination; and where, therefore, the needle is directed along the terrestrial meridian.

Source: wiktionary

It is contended by some that their [cyclones'] general movement is at right angles to the magnetic meridian. If this should prove to be correct, then in all that part of the United States lying west of the Agonic Line, the general direction whence local rain, hail, and snow-storms come, will be as many degrees north of west as the declination of the needle is east of north; and in all that part of the territory lying east of said Agonic Line, they will come from a direction as many degrees south of west as the declination of the needle is west of north.

Source: wiktionary

One of these [agonic lines] passes over the American and the other over the Asiatic continent, and the former has consequently been called the American and the latter the Asiatic agonic. […] On the west of the Asiatic agonic the declination is west, on the east it is east.

Source: wiktionary

It should be noted that the period of 2000 years deduced from the average motion of the agonics is identical with that which we obtain if we suppose that the secondary magnetic system revolves around the equator at the average rate of the two secondary poles, viz: ³⁶⁰⁄_(0.194) = 1860 years.

Source: wiktionary