December 21, 2011
To be posted on

Daniel Lathrop
University of Maryland
Institute for Research in Electronics and Applied Physics
Energy Research Facility, Bldg. #223
Paint Branch Drive
University of Maryland
College Park, MD 20742-3511

Dear Dr. Lathrop:
I was happy to read (Susan Young Dynamo Maker Ready to Role NATURE vol. 480 no. 7376 December 8, 2011 page 162) that you are planning to run a model of the internal dynamo that produces the earth’s magnetic field.  This is far from my area of greatest interest as you can tell by the name of my web site, but for many years I have wondered how such a mechanism could exist inside the earth.  Even giving the fact that it might create a self sustaining magnetic field by the slow swirling of matter within the earth, how then could it reverse?  I have even devised an alternative model.

I am somewhat surprised to see that the axis of your device is vertical, thus producing an asymmetric force gradient along the axis, which of course the earth does not have.  And there is no mention of whether the device is heated at the core, nor whether the surface is kept just cool enough for a crust to form.  But I am sure you have such details well in hand.

But I thought it might be fun to have an alternative model.  It might be easier to distinguish between two models than simulate one that simply has to be true.  So here is my model.  I do not insist on it; I merely describe it because I have not heard of it elsewhere.   The source of the magnetism might be atmospheric. 

Assume that there is little sustained wind at the equator and the poles and that the trade winds cancel each other out.  Then assume that wind, maybe carrying dust and leaves, creates a charge separation blowing across the ground.

This gives a moving charge, a current if you will, that is usually coming out of the west, born by the prevailing westerlies.  A circularly moving current produces a magnetic field at right angles to its own plane. 

If I may point out a couple of things without seeming to have espoused the idea too dearly: A change in vegetation cover might change to sign of the charge being carried, reversing the poles.  There are no prevailing westerlies on the sun, and its magnetic field is less organized.  If the effect is seen only over land, then one might not be surprised to find the alignment of the magnetic field with the rotational axis of the earth to be closer in the northern hemisphere than in the southern.  The effect could be from charge separation occurring in electrical storms (which of course might in turn be due to ground contact effects). 

That’s about it.  The thought nags me from time to time, and I certainly hope you lay it to rest soon, but I thought you might enjoy knowing it.


M. Linton Herbert MD

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