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Worldwide wavelet analysis of geomagnetic jerks

Abstract : Following an earlier study which gives the principles of the method and an example of application to the eastern component of the magnetic field in the European region [Alexandrescu et al., 1995], detection and characterization of geomagnetic jerks using wavelet analysis is generalized to any horizontal component of the field and to a worldwide distribution (involving 97 locations) of observations. This allows for a systematic and global search for such events within the twentieth century and makes it possible to unravel a number of intriguing properties associated with them. Whereas our first study only reveals five such events in Europe, we can now state that seven and only seven events have apparently occurred throughout the world during the present century. Two (1969 and 1978) are unquestionably of global extent, three (1901, 1913, and 1925) being possibly of similar extent, while the remaining two (1932 and 1949) are not seen everywhere at the Earth's surface. We confirm our early result that the events are more singular than previously thought, with a "regularity" systematically closer to 1.5 than to 2, and a common mean value of about 1.6. Furthermore, the 1969 and 1978 events display a two-step spatio-temporal behavior consisting of an "early arrival" in the northern hemisphere, a "late arrival" in the southern hemisphere, and a time lag between the two arrivals of the order of a couple of years. We were also able to show that the 1969 and 1978 events tend to at least partially balance each other. The extent to which this is true remains to be assessed, mainly because our method, although already providing some information about the geometry of the events, does not yet allow the proper recovery of their intensities.
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Mioara Alexandrescu, Dominique Gibert, Gauthier Hulot, Jean-Louis Le Mouël, Ginette Saracco. Worldwide wavelet analysis of geomagnetic jerks. Journal of Geophysical Research : Solid Earth, American Geophysical Union, 1996, 101 (B10), pp.21975-21994. ⟨10.1029/96JB01648⟩. ⟨insu-01401417⟩

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