Friday, November 25, 2011

The Magnetic Earth and Auroras--How it Works and Tantalzing Possibilities

So, I was reading about the magnetic stripes emanating from the mid-oceanic ridges and how they formed--by the poles reversing periodically over millions and thousands of years (It's timed irregularly.  Sometimes in as little as a few tens of thousands of years and other times making it 40 million years.)--and wondered something quite tantalizing...

If the auroras at the poles are caused by the magnetic field of the Earth (more on this below) then what would happen if the magnetic pole was in the process of switching?  Could there be auroras in the mid-lattitudes?  Could Los Angeles, Paris, Hong Kong, Abu Dhabi, Mexico City and Calcutta all get astronomical light shows temporarily?  Might I see Northern Lights right here in the South?  Laser light show in the sky over Florida?!?!  Just maybe!!  And, quite possibly, at any moment!  We're kind of due for a switch!!

Red is caused by nitrogen and green by oxygen.

Auroras are caused by charged particles (electrons and protons) flowing from the Sun hitting the upper atmosphere.  They hit the nitrogen and oxygen in the atmosphere and cause the electrons to become excited and then relax releasing photons.  They typically only happen at the poles because the Earth produces a doughnut shaped magnetic field and the charge on the particles are repelled by the doughy part of the doughnut and flow to the doughnut hole, which is at the poles.

Just like in a generator, magnets moving cause electric currents and electric currents cause magnetic fields to be created.  So, we can think of the metal core of the Earth as a big churning magnet that is caused both by the rotation of the Earth, convection and subduction--move the metal around and create a current that creates a magnetic field.  So, that's why the north pole is at the north and not on the equator or whatnot--the way the spin of the Earth causes a molten flow.

What triggers the switches?  It gets even more interesting!  Probably a lot of things, but one impetus could be asteroid impacts!  What are the effects of a switch?  Possibly mass extinctions!  Without the protective magnetic field we'd be bombarded with some pretty nasty charged particles from the Sun *and* since Earth's magnetic field also holds a significant amount of charged particles in place, in the Van Allen radiation belt, without the magnetic field a flood of charged particles would rain down.  This could have caused some of the mass extinctions in the past.  (But, it also might not have.  There's scant correlation between switching events and known extinctions event.  And no known switching event for the well known extinction of the dinosaurs.)

So, it might be a big cancer causer, but the light show could be amazing!


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