Definition

With “geomagnetic jerk” it is indicated a rapid change of inclination of the secular variation curve of one of geomagnetic fields components, which happens on a world scale during 1 or 2 years.
The first jerk was identified at the end of the 70’s. Since then, using different techniques, 8 more have been identified respectively in the years: 1901, 1913, 1925, 1932, 1949, 1969, 1978 and 1991. The secular variation (SV) of the Y component of the geomagnetic field as a function of time, from two different observatories, is shown in the figure. The SV trend clearly shows the presence of rapid inclination changes, thus of jerks, during the last century. Two more events are shown in the figure, (1938 and 1958) but not everyone identifies them as jerks.

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