Emission Electron Microscopy in combination with X? ray Circular Dichroism (TR-PEEM-XMCD) A study using Time Resolved Photo? Magnetization Dynamics in Spin Valves.

Although it is little more than a guess, it is thought that in over four billion years the temperature at the core has fallen by no more than 200б°F. No one knows exactly how hot the EarthБЂ™s core is, but estimates range from something over 7,000б°F to 13,000б°F-about as hot as the surface of the Sun. The outer core is in many ways even less well understood, though everyone is in agreement that it is fluid and that it is the seat of magnetism. The theory was put forward by E. C. Bullard of Cambridge University in 1949 that this fluid part of the EarthБЂ™s core revolves in a way that makes it, in effect, an electrical motor, creating the EarthБЂ™s magnetic field. The assumption is that the convecting fluids in the Earth act somehow like the currents in wires. Exactly what happens isnБЂ™t known, but it is felt pretty certain that it is connected with the core spinning and with its being liquid. Bodies that donБЂ™t have a liquid core-the Moon and Mars, for instance-donБЂ™t have magnetism. We know that EarthБЂ™s magnetic field changes in power from time to time: during the age of the dinosaurs, it was up to three times as strong as now ...»