Monday 27 Feb 2017: Waves in the Earth's core (Joint Astrophysics/GAFD seminar)
Prof. Chris Jones - University of Leeds
Seismology has given us a picture of the basic structure of the interior of the Earth, but it cannot tell us about the magnetic field or the flows inside the Earth's core. A large amount of geomagnetic data has come from satellites over the last forty years, which could potentially answer some major questions about the core. Is the core convecting everywhere, or are there stable layers near the core boundaries? What is the strength of the magnetic field in the core, and could there be a large hidden toroidal component which doesn't escape outside the core? The geomagnetic field varies with time, but are these variations caused by a steady flow advecting a complicated field, or is the variation a sign of waves in the core?
There are two main ways to address these issues: (i) direct numerical simulation of the geodynamo, and (ii) understanding the MHD wave motions in the core. These techniques can be applied to the core, but they can also be applied to a range of problems in astrophysical and geophysical fluid dynamics. In this seminar we review progress on rotating MHD waves in both adiabatic and stably stratified regions, and discuss how the identification of the wave modes is helping to resolve some of the fundamental issues. We also describe some recent work in which analysing the waves found in dynamo models is helping to bridge the gap between the complex theory of rotating MHD waves and observations.