Geomagnetic changes in polarity reversal
We have introduced KML files showing secular variations of 100, 400 and 7000 years. Nontheless the most drastic in the geomagnetic changes are reversal of geomagnetic polarity. polarity It is real turning of the mar magnet, so that the polarity of the geomagnetic field, the N pole in the Antarctic and the S pole in the Arctic today, turns over itself.
This phenomena, geomagnetic polarity reversals, were found and acknowledged until eary 20th century since several evicences had been discovered by B. Bruhns, M. Matuyama, and others.
The last reversal of the field occured about 780 thousand years ago. Before that, there were many reversals in the geomagnetic field polarity. People praised Brunhes and Matuyama for their contributions and the last two chrons of geomagnetic polarities, between present and 780 ky ago and between 780 ky ago and 2.6 My ago, have been named Brunhes normal chron and . Matuyama reversed chron, respectively.
Mistery of the geomagnetic polarity reversal, why and how do the reversals occur, is one of the biggest unsolved issue in the Earth sciences.
Couple of years ago, seveal groups proposed the geomagnetic chainge model during the last reversal, Brunhes - Matuyama polarity boundary (MBB), with compilation of the paleomagnetic data.
Technically speaking they are not enough and not complete models, instead, here we introduce one of them.
Following KML files indicate the magnetic field lines, countour maps radial component (Br) and inclination (I) on the Earth's surface, modeled by Leonhardt and Fabian (2007).
Screenshot: click to zoom up: Magnetic field lines and contour map of Br.
KML files: each contour map can be displayed with magnetic field lines at once.
- Magnetic field lines: MAGE05-3F_LF07MBB_20120308.kmz (22.3MB) Heavy!
*modified for latest versions of Google Earth (2012/03/08) - Radial comp. Br[nT]: MAGE05-3Br_LF07MBB_20101204.kmz (10.8MB)
- Inclination I[deg]: MAGE05-3Inc_LF07MBB_20101204.kmz (12.1MB)
Notice: We apologize that former version KML files (MBB-Reversal_MFL_20080515.kmz, MBB-Reversal_Br_20080519.kmz, MBB-Reversal_Inc_20080519.kmz) has fatal bugs and they doesn't work in the Windows / Mac OS environments. We have replaced wrong KML files by new ones. They become lighter and available even in netbooks with 1GB memory (2010/12/06)
Video of demo with commentary of download, open and usage of KML files
Here is video of stereographic view (parallel method).
It is easier for good view to try holding monitor at length of feets.
References:
Brunhes, B. Recherches sur le direction d'aimantation des roches volcaniques,
J. Phys., 5, 705-724, 1909.
Matuyama, M. On the direction of magnetisation of basalt in Japan, Tyosen and Manchuria,
Proc. Imp. Acad. Japan, 5, 203-205, 1929.
Leonhardt R. and K. Fabian,
Paleomagnetic reconstruction of the global geomagnetic field
evolution during the Matuyama/Brunhes transition: Iterative
Bayesian inversion and independent verification,
Earth Planet. Sci. Lett., 253, 172--195, 2007.
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