November 17, 2017 | David F. Coppedge

Anomalies in Planetary Magnetic Fields

Something is terribly wrong in the geodynamo theory for magnetic fields.

As Cassini scientists admitted (NASA and JPL), Saturn’s magnetic field contradicts theory. There is almost zero difference between the spin access and its magnetic field axis. Theory requires some degree of difference to drive the dynamo assumed to create magnetic fields. This “surprising” fact remains unexplained after Cassini’s 13-year mission.

Based on data collected by Cassini’s magnetometer instrument, Saturn’s magnetic field appears to be surprisingly well-aligned with the planet’s rotation axis. The tilt is much smaller than 0.06 degrees — which is the lower limit the spacecraft’s magnetometer data placed on the value prior to the start of the Grand Finale.

This observation is at odds with scientists’ theoretical understanding of how magnetic fields are generated. Planetary magnetic fields are understood to require some degree of tilt to sustain currents flowing through the liquid metal deep inside the planets (in Saturn’s case, thought to be liquid metallic hydrogen). With no tilt, the currents would eventually subside and the field would disappear.

Saturn is not the only planet with a magnetic problem.

Geophysical Research Letters posted a paper, “The case against an early lunar dynamo powered by core convection.” The authors figure, “we determine herein that there is insufficient energy associated with core convection – the process commonly recognized to generate long-lived magnetic fields in planetary bodies – to sustain a lunar dynamo for the duration and intensities indicated.”

Geophysical Research Letters also posted another anomaly, “Insufficient energy from MgO exsolution to power early geodynamo.” Notice the first sentence in the Abstract, and how the authors debunk a proposal to keep the dynamo going for the assumed age of the Earth:

The origin of Earth’s ancient magnetic field is an outstanding problem. It has recently been proposed that exsolution of MgO from the core may provide sufficient energy to drive an early geodynamo. Here we present new experiments on Mg partitioning between iron-rich liquid and silicate/oxide melt. Our results indicate that Mg partitioning depends strongly on the oxygen content in iron-rich liquid, in contrast to previous finding that it depends only on temperature. Consequently, MgO exsolution during core cooling is drastically reduced and insufficient to drive an early geodynamo alone.

At The Conversation, Christopher Davies titled his post, “Mysterious ‘geomagnetic spike’ 3,000 years ago challenges our understanding of the Earth’s interior.” This article mentions something important to know about magnetic field theories: “Most of our knowledge of the core derives from roughly the last 200 years, corresponding to the time when direct magnetic field measurements have been available.” Assuming anything about the magnetic field for 4.5 billion years, therefore, requires extrapolation of observations by 230,000 percent.

This is another area where scientific papers differ sharply from what is told the public. TV programs and school textbooks make it seem like magnetic fields are all figured out. Real scientists sweat over theories that don’t work.

A new book we will be announcing this weekend has a whole chapter on the problem of Earth’s magnetic field. Watch for it Sunday.

 

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