We live in the most comfortable of planets. It may not be very visible, but the Earth's magnetic field plays a critical role in maintaining that comfort. The remaining rocky planets in our Solar System have weaker magnetic fields and, as a result, are subject to a constant bombardment of high-energy particles from the Sun. Yes, our biosfos owe much to a pool of molten steel at the core of our planet.
However, the main one gives us a puzzle. The extreme conditions are very difficult to understand: we cannot conduct experiments that perfectly mimic the conditions of the main, and our measurements are indirect, because no one wants to visit the main. That leaves us with computer models. Until recently, these models were rather limited. However, the ever-increasing computational power is beginning to show that the mainstream has an interesting story to tell. The mass accumulation during its growth came through the great impact and ocean of molten rock. Gravity provided a type of filter: heavy elements such as steel were obtained at the core, while light elements such as silicon and oxygen were left floating above.
The simple picture provides the basic stratification of the Earth, but it does not explain the magnetic field. To do that, you need to include the assembly, which drives the waves of liquid steel that form a magnetic field. The assembly, however, requires a temperature difference between the center of the core and its outer boundary. But the heat conductivity of a cast iron makes it difficult to imagine that the difference in temperature is sufficient to obtain assembly.
To muddy additional liquid steel, convection currents indicate a certain amount of mixing. So, we have several different play processes: gravity drive stratification while convection mixes in layers. Then, as the elements are mixed, solubility and chemical reactions are played out. Is oxygen retained in the early phase thanks to solubility and chemical reactions? Does the presence of oxygen change the flow of heat, which then changes the strength of the magnetic field?
To understand these processes, you need to perform a very difficult set of calculations. First, the properties of the chemical quantities of the elements need to be calculated to determine what is the minimum energy adjustment of a mixture ̵1; how much oxygen should be iron. The calculation then needs to combine how the elements and molecules move. All these calculations need to be carried out at a temperature of about 5,000K and pressures of 160GPa.
Take to GPUs
Twenty years ago, you couldn't combine these calculations in any useful way, simply because they were not computational enough. Ten years ago, these calculations would survive under very limited circumstances. And now they can be applied to temperatures and pressures related to the Earth's core and large enough to be significant (albeit at a very small scale). basic. Researchers have shown that the early phase probably contains more oxygen than the primary one today. However, oxygen that can have a stratified layer of oxide (even at these temperatures, probably better think of it as a mixture of iron and oxygen) is just below the boundary between the core and the mantle. The stratification and accompanying reaction reduced the amount of heat flow outdoors. This, in turn, weakens the connection fingers that drive the circulation required for the formation of the Earth's magnetic field. , although the main results of their results are reliable, some of the conclusions are weak. For example, the partitioning of iron and oxygen containing iron is stable. However, the model does not have sufficient size to determine whether the stratification is stable when exposed to convection currents in the core and thermal gradients in the mantle above. These types of calculations require a different type of model.
Researchers also did not include the influence of silicon and magnesium in their calculations. These are the other two major contributing elements and could significantly change the results. Researchers treat their calculations as a proof-of-principle for the method. The next step is to perform a new set of calculations with a more realistic mix of elements. Then we can get a clearer picture of the chemistry of the main part of the Earth.
Physical Review X, 2019, DOI: 10.1103 / PhysRevX.9.041018 (About DOIs)