Atmospheric mass redistribution result in very slight annual changes to the speed of rotation of the Earth. The seasonal variational in the mass of snowfall is part of that process. Most ice in the Arctic is floating so it makes little difference to the mass distribution. Longer term changes in the Antarctic or Greenland icecaps may result in a slight axial change but it is not going to do much to the magnetic field from the core.
jim hardy said:
everybody seems to look inside not outside.
I think it a mistake to think of the core as an immediate field generator. The Earth must contain a historical collection of magnetic fields, interlocked with circulating electric currents, on and in the conductive core. It takes a long time for things that big and conductive to change. Even if it did not generate the field, the core would be a good place to store a field. I think we need to keep an open mind rather than hang our hat on anyone simple theory.
jim hardy said:
What happens if, as in a simplified Earth's atmosphere
two concentric spherical shells of charge are separated by 50 km
and there's an E-field between the shells , Earth's is a few hundred volts per meter
and the shells rotate rotate in lockstep
1. Does a magnetic field result?
2. Is it in same direction as Earth's?
We can try to apply magnetohydrodynamics (MHD) to the atmosphere.
Simply put, there is a magnetic field from a N magnet pole in the Antarctic where the penguins are, to a S magnet pole in the Arctic where the bears are. (Remember that a North magnet pole is one that seeks the North of the Earth, so the Earth's Arctic must actually be a S magnet pole).
There is also a dominant West to East atmospheric circulation. There are also four jet streams flowing from West to East at speeds of a few hundred km/hr. Those streams are driven by Earth rotation.
https://en.wikipedia.org/wiki/Jet_stream
Now imagine embedding a dust or pollen particle in the atmosphere, then ionise it with UV radiation from sunlight. That will provide a supply of ions. Man-made dust and pollen released by farming practices along with smoke pollution from industrial regions will also provide particles for ionisation.
The force due to the cross product of the moving ions in the atmosphere, by the Earth's magnetic field, will tend to move free electrons and negative ions downwards while it lifts positive ions. That will tend to sort the charges and is consistent with the polarity of the Earth electric field. Over time the polarity of Earth-Ionosphere charge will be reinforced with more positive charges being concentrated in the ionosphere, while electrons end up on the Earth's surface. At some point we can expect a “sprite like” dielectric breakdown of the atmosphere that will limit the voltage gradient.
https://en.wikipedia.org/wiki/Sprite_(lightning)
Such an atmospheric MHD charge pump may be sufficient to provide the electrification needed for thunderstorms. When MHD is considered, there seems to be less requirement for graupel collisions in thunderheads to explain the electrification of the atmosphere.
What are the implications of such an MHD interaction? We must expect both generator and motor effects from atmospheric MHD. Rain falling through the stationary cloud base can be expected to fall diagonally due to the charge on the nuclei that seeded the falling drops. We can also expect a slight deflection of the Earth magnetic field due to the mass of atmosphere being deflected as the distributed charge moves.
If the direction of the Earth's magnetic field and the polarity of the ionosphere is intimately linked by MHD through the jetstreams and general atmospheric circulation, how could we possibly test such an effect?
If the magnetic field was to reverse, would we see a reversal of Earth-Ionosphere electric polarity? Could the positive ions fall to Earth while electrons rise to the ionosphere? That might significantly change the availability of nuclei for rain drop formation. We could look for historical precipitation evidence. By drilling deep into the Antarctic icecap we could look at rates of precipitation around the time of the last magnetic change, about 800k years ago. Unfortunately the deepest holes drilled so far hit rock at about that time, so do not reveal the data needed to test such a reversal hypothesis. There is a search under way in the Antarctic for ice cores that go back to one million years. If such cores are found there will then be evidence. If such cores are not found then we have two obvious possibilities; evidence is lost because the weight of accumulated ice is sufficient to melt the base of the icecap where it contacts the rock, and/or ice did not start to accumulate in the Antarctic until the last magnetic reversal. The climate implications of such a magnetic reversal effect, if it occurred, could be very significant. We need data. Might rainforests change places with deserts?
jim hardy said:
might there be more going on up there than we think?
I do not expect Earth's magnetic field to be induced and accumulated in the core by the motion of atmospheric charge, but it is certainly coupled to some extent.
Yes, there is more going on than is admitted in the simple theories. This is a field of science that is ripe for exploration.
