|MadSci Network: Earth Sciences|
Berry, You are proposing a rather difficult project. A method for developing a theoretical estimate of how the energy from a magnetic storm is split between the core and the magnetosphere is not obvious. The studies of magnetic storms I have found all pretty much ignore the core. While a magnetic storm can create a million ampere “Ring Current” in the Van Allen Belts and raise the ion temperature thousands of degrees, it is pretty thin stuff up there. Dumping the same amount of energy into the core would hardly change the temperature at all. Your question does touch on why the Earth has a magnetic field at all. Glatzmaier and Roberts’s papers on the geodynamo model produce a self sustaining magnetic field that depends on a differential rotation of the inner core and the rest of the Earth, convection currents in the outer core and variable heat flow from the core to the mantle. The differential rotation has been observed in seismic studies. Your second question is not much easier. There have been a number of papers written attempting to reconcile thermodynamic theory with seismic velocity, gravity and heat flow measurements. There is only a rough consensus on the relative contributions of accretion energy and radioactive heat production. The distribution (location) of the radioactive heat production differs considerably between models. Different models disagree as to whether the mantle convects from core to Moho in a single zone or at least two zones. If there is a single zone the mantle will overturn in about 300 million years. The short answer to your second question is hundreds of millions of years. There are quite a few web sites devoted to the nature of the structure of the Earth and it’s magnetic field. A disturbing number of them are nonsense. A few web sites that may be of interest are http://es.ucsc.edu/~glatz/geodynamo.html, http://www.phy6.org/earthmag/dynamos2.htm, http://www.nasa.gov/vision/earth/lookingatearth/29dec_magneticfield.html, http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magearth.html, http://www.mantleplumes.org, http://www.geomag.bgs.ac.uk/earthmag.html and http://www.sec.noaa.gov. David
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