secular variation
Field changes slowly
Secular variation refers to gradual, long-term changes in a measured quantity, as opposed to periodic or random fluctuations.
The term appears most often in geophysics, where it describes the slow drift of Earth's magnetic field over decades or centuries: Secular variation makes old compass readings unreliable.
In astronomy, it refers to cumulative changes in orbital elements.
The secular distinguishes these trends from cyclical patterns that repeat.
- paleomagnetismRemnant magnetism in rocks
- magnetic fieldForce zone around magnets
- declinationAngular distance from equator
- isogonicHaving equal angles
- compass needleMagnetized directional indicator
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- paleomagnetismpaleomagnetism, reversed polarity, remanence, excursion, excursions