Decoding Geomagnetic ReversalsThe natural magnetic field of our planet is generated by complex motio

Decoding Geomagnetic ReversalsThe natural magnetic field of our planet is generated by complex motions of molten iron alloys - 2,900 kms deep in the outer core. The most fascinating feature of the Earth’s magnetic field is its ‘reversals’ that occur on irregular timescales ranging from days to millions of years. During a magnetic reversal – the north and south magnetic poles switch places. Reversals are rare events when we compare their duration (~1000 years) to the length of the polarity intervals (upto millions of years). Records of these reversals can be decoded from magnetic-grains in volcanic lavas and sediments as they lock-in the Earth’s magnetic field the time they were cooled on the surface of the Earth or were deposited at the bottom of the ocean. Paleomagnetists have spent the last 50 years going through these geological records and preparing a timescale of the magnetic reversals. However, the paleomagnetic record lacks detail especially during the reversal event. These events are geologically ‘rapid’ that it lacks sufficient temporal resolution in the geological record – sediments. Furthermore, during such reversal events the Earth experiences a weak magnetic field intensity, and this affects the precision of the magnetic recording in the sedimentary records. On the other hand, volcanism is random in nature with lava flows unevenly distributed in time. Moreover dating lava flows comes with an error bar that exceeds the duration of the magnetic reversal and so cannot be accurately pinned down. Hence, the results from the geological record can be biased by artifacts and so such observations have generated controversy over the years.Advances in computational mathematics and numerical simulations have enabled us to gain new insights into the mechanism of the geodynamo and its reversals. Numerical simulations have generated hundreds of reversals too and some of them are similar to the geological record. During such cases we can compare and analyze the data and simulations together.Although magnetic reversals are poorly understood at the moment, most geophysicts would agree that the geomagnetic field is maintained by convection within the core which results in rapid motions of the iron-rich fluid in the outer core. We have also come to the agreement that no external forcing is required for a reversal and so a reversal is considered a fundamental property of the Earth’s dynamo.NateImage: http://bit.ly/2cf2NARSource: http://bit.ly/2ckS2jKOriginal Paper: http://bit.ly/2bJSbvp -- source link

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