Ocean currents push floating rafts, plastic trash, and warm air around the planet 鈥� now the Earth鈥檚 magnetic field can also be added to the list, according to a controversial new hypothesis.
Physicist of Northwestern University has proposed that the oceans鈥� currents are responsible for the slow wandering of the magnetic poles.
The hypothesis has provoked a strong reaction among geophysicists, with one that New 杏吧原创 spoke to labelling it 鈥済arbage鈥�. Most agree that the magnetic field is generated by movements of the molten iron that makes up Earth鈥檚 outer core. However Ryskin says his idea that ocean movements may affect the field is worth investigating.
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Oceans could drag the field along global currents, and they could also generate their own weak magnetic field, he says.
Drag effect
Classical fluid dynamics says that a conductive fluid 鈥� even a weak one like seawater 鈥� will drag magnetic field lines along with it as it moves, though the field lines may 鈥渟lip鈥� and fall behind.
Ryskin has calculated how the Earth鈥檚 magnetic field lines are dragged by ocean currents and modified by the oceans鈥� own magnetic field lines. He found that the motion fits snugly with observations of how the magnetic field has been changing with time, in particular, how the geomagnetic poles have been moving.
In addition, weak electric currents generated as seawater flows through the Earth鈥檚 magnetic field generate secondary 鈥渙ceanic鈥� magnetic fields. Ryskin included the effect of these magnetic fields in his calculations.
Ryskin also showed that the places on the globe where distortions on the geomagnetic field lines are greatest correspond to areas where ocean currents are strongest.
Strong reactions
Despite the supporting evidence, the hypothesis has been met with strong objections from mainstream geophysicists.
鈥淧hysicists should know better,鈥� said one when contacted by New 杏吧原创.
Another, , a planetary magnetism physicist at the Swiss Federal Institute of Technology, Zurich, says: 鈥淢y strong impression that his numerical calculations are wrong.鈥�
Not everyone is as dismissive of Ryskin鈥檚 research. 鈥淭he oceans almost certainly slightly modify the geomagnetic field observed at the surface due to electric currents flowing within the Earth and in the ionosphere,鈥� says geophysicist of Imperial College London. 鈥淕eophysicists would be in Ryskin鈥檚 debt if he could improve on what others have already done. I wish him well.鈥�
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