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Abstract

The Earth's magnetic field is generated mainly by a self-sustaining dynamo in the fluid outer core. Known as the core or main field, the dynamo's magnetic field is not constant but changes with time, a phenomenon denoted as secular Variation. Unfortunately, no common agreement exists about the definition of secular Variation: While some use this term for the temporal changes of the core field in general, others use the term only for its linear part (first time derivative). Two more terms are linked to core field temporal variations: geomagnetic jerks and archeomagnetic jerks. They are used to describe specific magnetic field signatures in the observations, implying a phenomenological classification. We suggest that a characterization of magnetic field changes based on the physics of the underlying core process may be more useful. Such a classification is proposed here to help avoid further misunderstanding through terminology.