"Field reversal" refers to the change in direction or orientation of a magnetic or electrical field. It means that the normal flow or polarity of the field has been reversed. Full definition
(2), and the polar field reversal around that period. (swsc-journal.org)
However, it does suggest that the present - day pattern may be the latest manifestation of a repeating feature that occasionally leads to a global field reversal. (sciencedaily.com)
Which could account for our planet's weird history of magnetic field reversals, with north and south poles swapping places. (discovermagazine.com)