The Earth's magnetic field is generated by fluid flow at the Earth's metallic liquid outer core, in a process known as the geodynamo.
Because of its current strength and mainly dipolar geometry, the geomagnetic field efficiently organizes the way energetic particles flow in the vicinity of the Earth. Those particles mainly originate from the solar wind and may occasionally and regionally reach the Earth's atmosphere. Were it not for the Earth's magnetic field, they would directly reach the atmosphere.
The geomagnetic field however decays by a rate 10 times faster than the rate of free decay, and displays a large area of even faster-growing weakness (on a decade time-scale), known as the South Atlantic Anomaly, where more and more of those particles are to be found, increasing the danger for both manned space missions and satellites.
Understanding the mechanisms responsible for this rapid evolution is both a practical issue - providing some input for space scientists to predict the future areas of dangers in the space environment - and a fundamental one - understanding the inner working of the geodynamo.
The objectives of this research are more specifically to study the possible influence of core-mantle interactions
- in defining the main characteristics of the current geomagnetic field,
- in governing the evolution of the geomagnetic field.
These goals will be achieved using an approach combining data analysis and numerical simulation. Such a combined approach has seldom been used so far, but is now finally accessible for extensive studies, thanks to the availability of more and more high quality geomagnetic and seismological observations, and of much more affordable dynamo numerical codes.
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