Details of Award
NERC Reference : NE/C51889X/1
The temperature of the Earth's core from highly precise quantum mechanics calculations.
Grant Award
- Principal Investigator:
- Professor D Alfe, University College London, Earth Sciences
- Grant held at:
- University College London, Earth Sciences
- Science Area:
- Earth
- Overall Classification:
- Earth
- ENRIs:
- None
- Science Topics:
- Properties Of Earth Materials
- Mantle & Core Processes
- Abstract:
- We learn from very young that our planet is surrounded by what is called the Earth's magnetic field. This feature has been exploited by navigators in the past, although is less important for this purpose in our days. More importantly though, the presence of the Earth's magnetic field is one of the amazing coincidences that make our planet habitable to life in the form we know it. The reason is that it acts as a shield against the deadly solar wind. Unfortunately, we also know that this magnetic field is not constant, but changes direction in time and, more importantly, its intensity vanes. The reason why this happens is that this magnetic fields is generated dynamically by the swirling of iron in the liquid part of the Earth's core, some 4000 Km below our feet, and these whirlpools are not permanent features but change with time. In particular, one very important question is why are these whirlpool there at all, where does the energy to sustain them come from. The answer to this question lies in the core itself, and in particular in the fact that as the planets cools down, the liquid core gradually solidifies, leaving a solid inner core in the centre of the Earth. In fact, the core of the Earth's is not formed by pure iron, but by a mixture of iron together with some light impurity like oxygen, sulphur or silicon. As the core solidifies, an almost pure iron solid is formed at the centre, and therefore these light impurities are released outwards in the liquid. Since they are lighter than iron, they raise towards the surface of the core, and in doing so they stir the liquid and support the whirlpools. A portion of the energy which supports these whirlpools also come from the latent heat of fusion, which is also released by the solidification process. If we want to understand well how these convective motions in the outer core work, and therefore try to predict how the magnetic field will evolve in the future, we need to build a model. One crucial parameter for any model is the temperature of the core. One way of estimating this is to exploit the presence of a solid and a liquid core: at the boundary between solid and liquid the two phases coexist, and therefore they must be at the melting temperature. Since the core is mainly made by iron, and since we know that the pressure at this boundary is 329 millions of atmospheres, it follows that knowing the melting temperature of iron at 3.29 millions of atmospheres will provide the answer we are looking for. A number of experiments have attempted to measure the melting temperature of iron at these conditions, but these extremely high pressures make it very difficult to perform these experiments (in the centre of the Earth the pressure is so high that the volume of iron is squeezed to almost half its value at atmospheric pressure), with a resulting large disagreement between the results of different laboratories. An alternative to experiments is to perform theoretical calculations. In a sense this is an easier approach, as we do not have to subject a sample to the conditions of the Earth's core. However, one crucial question us, of course, how accurate and reliable would the calculations be. A number of groups, including our self, have already tiled to calculate the melting curve of iron under Earth's core conditions, and the results between different groups also showed marked differences. One possible reason of these disagreement is the number of approximations used by the different groups: unfortunately we do not yet have an 'exact' theory which can routinely be applied, so we have to rely on a number of approximations. The main objective of this proposal is to develop a very accurate technique, based on quantum Monte Carlo calculations, which will be at least 10 times more accurate than any theory used before, and apply this technique to calculate, very precisely, the melting temperature of iron at 3.29 millions of atmosphere.
- NERC Reference:
- NE/C51889X/1
- Grant Stage:
- Completed
- Scheme:
- Standard Grants Pre FEC
- Grant Status:
- Closed
- Programme:
- Standard Grant
This grant award has a total value of £169,195
FDAB - Financial Details (Award breakdown by headings)
| Total - Staff | Total - T&S | Total - Other Costs | Total - Indirect Costs |
|---|---|---|---|
| £109,866 | £6,206 | £2,585 | £50,538 |
If you need further help, please read the user guide.