You searched for: “geomagnetic variations”
geomagnetic variation (s) (noun), geomagnetic variations (pl)
Any change that happens to the geomagnetic field: A geomagnetic variation can be temporal or short-time changes in the geomagnetic field, both long-term (secular) and short-term (transient).
This entry is located in the following units: -ation, -ization (-iz[e] + -ation); -isation (British spelling variation) (page 45) geo-, ge- + (page 14) vari- (page 1)