Download >>> https://byltly.com/25qb83
Scientists now believe that Earth's magnetic field may flip on the same schedule as the sun's - every 11 years. The main change would be to zones of magnetic intensity, but it could also mean that eventually, compasses might point south instead of north. A new study in "Nature Physics" reports details about what is called geomagnetic reversal, and says that each reversal provides its own surprises. "We can now prove that the last reversal was a global one," lead author Frédéric Deschamps, a geophysicist at the Paris Diderot University, told OurAmazingPlanet. "It's always been hard to prove that the geomagnetic field has reversed in the past because you need to find material whose magnetism was locked in at the time of reversal and is still preserved. Many scientists maintain this is impossible — it can't be preserved — but we found an excellent site and proved that it's possible." Scientists have long known that Earth's magnetic field flips its polarity every few hundred thousand years. They have also known that this has happened at roughly regular 11-year intervals for the last 90,000 years. It's not known why it happens at regular intervals, but scientists have proposed several possible mechanisms, including the idea that Earth's magnetic field is generated by electric currents generated deep inside Earth. As these currents wax and wane with time, so too might the magnetic field they create. Reversals could occur when the electric current flowing through these deep conduits reverses. On average, researchers say two geomagnetic reversals occur every million years. But measurements of ancient rock deposits tell a different story about what happened 3 million years ago. "We have found the signature of a complete reversal of the geomagnetic field in rocks which are 3.5 million years old, but this reversal happened at a time when the sun wasn't reversing its cycle, so it couldn't have been driven by changes to our star," Deschamps said. "This means there are still mechanisms to be discovered." The new study focuses on previous work that identified an 11-year cycle for reversals in sunspots. The sunspot cycle governs how much energy reaches Earth, but that doesn't seem to correlate with changes to Earth's magnetic field. But solar flares, which can sometimes intercept the sun's magnetic field, can be affected by changes in Earth's magnetic field, according to research on the topic. So scientists have asked whether there is some connection between sunspots and Earth's magnetic field. The new study concludes that there is. "It seems that the cycle of decreasing magnetic intensity in sunspots is somehow associated with increasing intensity on Earth," Deschamps said. The new 11-year cycle for geomagnetic reversals matches predictions made by a mathematical model of magnetic fields on Earth, based on records of past reversals. eccc085e13
コメント