INSTABILITY OF SECULAR VARIATIONS IN THE HORIZONTAL COMPONENTS OF THE GEOMAGNETIC FIELD: QUASI-PERIODIC FLUCTUATIONS AND JERKS
A.V. Ladynin
Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
Keywords: Geomagnetic field, horizontal components, secular variation rate, quasi-periodic fluctuations, periods of fluctuations, amplitudes of fluctuations, jerks
Abstract
Two types of fluctuations, with a short period (SPFs, 3 ± 0.15 years) and with a long period (LPFs, 10-70 years), have previously been found in the secular variation rate (SVR) of the horizontal component H , the vertical component Z, and the inclination I of the geomagnetic field (GMF) . The fluctuations of SVR for the horizontal components of the GMF ( X, Y , and D ) and the periods and amplitudes of their SPFs are estimated in this study. The SVR fluctuations for Y and D are synchronous and have identical phases, and the SVR fluctuations for X are opposite to them in phase, except the areas near the magnetic poles. The SPF periods for X , Y , and D are almost the same (2.8 ± 0.14 years). Jerks in the SVR of Y, especially significant in Europe in 1969 and 1978, were studied. It is shown that jerks are a component of long-period fluctuations in the SVR of Y; they appear at the coincidence of extrema of the same sign in LPFs and SPFs. Jerks need not be considered as a special phenomenon because they can be represented as the sum of quasi-periodic LPFs and SPFs.
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