RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 7, ES3003, doi:10.2205/2005ES000175, 2005
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[10] The analysis of the paleointensity data variation during and in the vicinity of the reversals showed that the average decline of the magnetic field during its reversals had been as high as seven times [Gurarii, 1988]. This estimate was obtained for the reversals of the last 15 million years, using the data published prior to 1986. As new data were published, including the detailed descriptions of the near-reversal variations of the geomagnetic field, this estimate did not experience any substantial changes [Gurarii et al., 2000a; Hartl and Tauxe, 1996], to name but a few.
[11] At the same time, an interesting result was obtained, which calls for its verification at the present-day level of data accumulation. It appears that the coefficient of the magnetic moment decline during reversals is controlled by the M value of the stationary field before its reversal [Petrova and Sperantova, 1986]. S. I. Braginskii advanced the suggestion (during some oral discussion) that various parts of the magnetic (dipole and nondipole) field show their different reactions to the reversal. The pre-reversal dipole field of a variable intensity declines slowly almost to zero, and a new field arises in an opposite direction, the nondipole field varying to a significantly lower degree. In other words, no dipole field could exist during the fairly long time of the pole switching. This view offered by S. I. Braginskii agrees with the conclusions advanced by Gurarii [1988], Clement [2004], and other authors, and is of great interest in terms of the physical nature of the dipole and nondipole field.
[12] As follows from the estimates of most of the authors, the time interval of some low M existence was notably longer than the time of the magnetic field reversal. The modal values of the Late Cenozoic reversals, estimated from the data available prior to 1986, suggested the average duration of the reversals to be 7-8 thousand years (the individual estimates varying from 4 to 25 thousand years), the time interval of the declining magnetic moment being 1.5 to 2.0 time longer, that is, embraced a time interval of up to 16 thousand years [Gurarii, 1988]. Merrill and McFadden [1999] estimated the time necessary for a complete reversal to be 1 to 8 thousand years. Clement [2004] concluded that the period of the four latest reversals had been 7 thousand years. This author noted that the duration of the field sign change had varied as a function of the latitude of the study area, which agrees with the simple model assuming that the dipole field declined to zero during its reversal and recovered again in the continuous presence of some nondipole field. This allows one to assume that the average time of a dipole field absence during inversions (if this is correct) was at least shorter than 7-8 thousand years.
Citation: 2005), Geomagnetic field reversals: Main results and basic problems, Russ. J. Earth Sci., 7, ES3003, doi:10.2205/2005ES000175.
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