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Geomagnetic jerk
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<h2 id="description">Description</h2> <p>Jerks seem to occur in irregular intervals, on average about once every 10 years. In the period between jerks, each component of the field at a specific location changes with time <i>t</i> approximately as a fixed <a href="/facts/Polynomial/Lzak8VVx">polynomial</a> of the second degree, <i>A</i> <i>t</i>2 + <i>B</i> <i>t</i> + <i>C</i>. Each jerk is a relatively sudden change (spread over a period of a few months to a couple of years) in the <i>A</i> <a href="/facts/Coefficient/5Hwq2Wuq">coefficient</a> of this formula, which determines the second derivative; and usually in <i>B</i> and <i>C</i> coefficients as well. </p><p>The strength of each jerk varies from location to location, and some jerks are observed only in some regions. For example, the 1949 jerk was clearly observed at <a href="/facts/Tucson/26QPvEaG">Tucson</a> (<a href="/facts/North_America/djNjCQIl">North America</a>, <a href="/facts/Longitude/HsC61ML9">long.</a> 110.93°), but not at <a href="/facts/Chambon-la-For%C3%AAt/7lWwtln7">Chambon-la-Forêt</a> (<a href="/facts/Europe/DTAtrKfh">Europe</a>, long. 2.27°). Moreover, the global jerks seem to occur at slightly different times in different regions; often earlier in the Northern hemisphere than in the Southern hemisphere.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> </p> <h2 id="theories">Theories</h2> <p>These events are believed to be caused by changes in the flow patterns of the liquid <a href="/facts/Earth%27s_outer_core/1U5pw3La">outer core of the Earth</a>,<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> as for instance carried by hydromagnetic waves such as torsional oscillations.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a><a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> Numerical simulations of core dynamics have successfully reproduced the characteristics of well documented jerks.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> In these simulations, jerks are caused by <a href="/facts/Alfv%C3%A9n_wave/t1xtbVuf">Alfvén waves</a> emitted inside the <a href="/facts/Earth%27s_outer_core/1U5pw3La">outer core</a> and focusing at the core surface. Prior to these explanations there had also been claims that geomagnetic jerks were connected to strong earthquakes.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Levantine_Iron_Age_Anomaly/Q20h26bw">Levantine Iron Age Anomaly</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>De Michelis, Paola; Tozzi, Roberta; Meloni, Antonio (2005). "Geomagnetic jerks: observation and theoretical modeling" (PDF). Memorie della Società Astronomica Italiana. 76: 957–960. Retrieved 16 September 2019. <a href="http://sait.oat.ts.astro.it/MSAIt760405/PDF/2005MmSAI..76..957D.pdf" target="_blank">http://sait.oat.ts.astro.it/MSAIt760405/PDF/2005MmSAI..76..957D.pdf</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Courtillot, Vincent; Le Mouël, Jean-Louis (10 June 1976). "On the long-period variations of the Earth's magnetic field from 2 months to 20 years". Journal of Geophysical Research. 81 (17): 2941–2950. doi:10.1029/JB081i017p02941. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Courtillot, V.; Le Mouël, J. L. (October 1984). "Geomagnetic secular variation impulses". Nature. 311 (5988): 709–716. doi:10.1038/311709a0. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>De Michelis, Paola; Tozzi, Roberta; Meloni, Antonio (2005). "Geomagnetic jerks: observation and theoretical modeling" (PDF). Memorie della Società Astronomica Italiana. 76: 957–960. Retrieved 16 September 2019. <a href="http://sait.oat.ts.astro.it/MSAIt760405/PDF/2005MmSAI..76..957D.pdf" target="_blank">http://sait.oat.ts.astro.it/MSAIt760405/PDF/2005MmSAI..76..957D.pdf</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Mandea, Mioara; Bellanger, Eric; Le Mouël, Jean-Louis (December 2000). "A geomagnetic jerk for the end of the 20th century?". Earth and Planetary Science Letters. 183 (3–4): 369–373. doi:10.1016/S0012-821X(00)00284-3. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Olsen, Nils; Mandea, Mioara (March 2007). "Investigation of a secular variation impulse using satellite data: The 2003 geomagnetic jerk". Earth and Planetary Science Letters. 255 (1–2): 94–105. doi:10.1016/j.epsl.2006.12.008. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Olsen, Nils; Mandea, Mioara (March 2007). "Investigation of a secular variation impulse using satellite data: The 2003 geomagnetic jerk". Earth and Planetary Science Letters. 255 (1–2): 94–105. doi:10.1016/j.epsl.2006.12.008. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>De Michelis, Paola; Tozzi, Roberta; Meloni, Antonio (2005). "Geomagnetic jerks: observation and theoretical modeling" (PDF). Memorie della Società Astronomica Italiana. 76: 957–960. Retrieved 16 September 2019. <a href="http://sait.oat.ts.astro.it/MSAIt760405/PDF/2005MmSAI..76..957D.pdf" target="_blank">http://sait.oat.ts.astro.it/MSAIt760405/PDF/2005MmSAI..76..957D.pdf</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Mandea, Mioara; Bellanger, Eric; Le Mouël, Jean-Louis (December 2000). "A geomagnetic jerk for the end of the 20th century?". Earth and Planetary Science Letters. 183 (3–4): 369–373. doi:10.1016/S0012-821X(00)00284-3. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>De Michelis, Paola; Tozzi, Roberta; Meloni, Antonio (2005). "Geomagnetic jerks: observation and theoretical modeling" (PDF). Memorie della Società Astronomica Italiana. 76: 957–960. Retrieved 16 September 2019. <a href="http://sait.oat.ts.astro.it/MSAIt760405/PDF/2005MmSAI..76..957D.pdf" target="_blank">http://sait.oat.ts.astro.it/MSAIt760405/PDF/2005MmSAI..76..957D.pdf</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Bloxham, Jeremy; Zatman, Stephen; Dumberry, Mathieu (November 2002). "The origin of geomagnetic jerks". Nature. 420 (6911): 65–68. doi:10.1038/nature01134. PMID 12422214. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Aubert, Julien; Finlay, Christopher C. (21 April 2019). "Geomagnetic jerks and rapid hydromagnetic waves focusing at Earth's core surface" (PDF). Nature Geoscience. 12 (5): 393–398. doi:10.1038/s41561-019-0355-1. ISSN 1752-0894. <a href="https://hal.archives-ouvertes.fr/hal-02129842/file/jerks-submitted.pdf" target="_blank">https://hal.archives-ouvertes.fr/hal-02129842/file/jerks-submitted.pdf</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Florindo, Fabio; De Michelis, Paola; Piersanti, Antonio; Boschi, Enzo (2005). "Could the Mw = 9.3 Sumatra earthquake trigger a geomagnetic jerk?". Eos, Transactions American Geophysical Union. 86 (12): 123. doi:10.1029/2005EO120004. <a href="https://doi.org/10.1029%2F2005EO120004" target="_blank">https://doi.org/10.1029%2F2005EO120004</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> </ol>