Courtesy photoThere may be more to the Earth’s magnetic field than commonly thought, says Cal Poly physics professor emeritus Kenneth Hoffman.
New research published in the weekly Science Magazine, by Hoffman and geochemistry professor Bradley Singer of the University of Wisconsin-Madison, suggests there is a second source of energy in the Earth’s magnetic field.
For Hoffman, publishing these findings is the culmination of over 30 years of research trying to better understand the earth’s magnetic field. Specializing in paleomagnetism, or the study of the magnetic field of a rock, Hoffman has worked with Singer since they met during a 1994 scientific conference. While the two specialize in separate fields, Singer’s work as a geochronologist is the perfect compliment for understanding magnetic fields. They have collaborated for such a long period that Hoffman now holds a position as a researcher at Singer’s university as well.
Based on their field work, taking core samples from ancient lava flows in Tahiti and West Eifel, Germany, the duo examined the mechanism that causes the main magnetic field, called the axial dipole, which acts essentially as a giant bar magnet and reverses the earth’s polarity. The last time such a flip occurred was 780,000 years ago, setting what we know as the magnetic North and South poles.
“The bottom line is that the Earth’s magnetic field, in geologic time, half the time your compass would point to the north and half the time it would point to the south. The understanding of this in the most direct way possible comes from rocks,” Hoffman said.
“We’re specifically looking at lava flows in this research that capture this period of time where the axial dipole is extremely weak and this second field is emerging. The spatial pattern that we found is very site specific,” Singer said.
“We’d like to have a lot more complete set of observations over a longer distance across the surface of the Earth and more records spanning a larger time scale but this is our hypothesis at the moment. We’d like to have more and better records,” Singer said, adding, “The grant would help us find records that are quite a bit older.”
In the mean time, these findings may give other scientists, using computer modeling of the Earth’s magnetic fields, a more complete picture.
“If it’s the case that these two fields can be described mathematically as an independent model, it could be viewed in a sort of simplified way that would then aid the description of the physics that go into computer models,” Cal Poly physics professor John Jasbinsek said.
He pointed out that it’s worth while to understand more about the way the magnetic fields work simply because, “if there’s no magnetic field, then there are no people.”
The pair is working on another grant from the National Science Foundation, which funded their current research, for an expedition to find samples in Australia and New Zealand next year.