Speaker
Paul Roberts
Description
The coupling of the Earth's core and mantle is responsible
for the largest fluctuations in the length of day. The
torques exerted by the core on the mantle are of order 10^18
Nm and are due to viscosity, core-mantle topography, gravity
and magnetic field. This talk will focus mainly on
gravitational and magnetic coupling, either or both of which
might explain the semi-decadal periodicity observed in the
length of day record. The magnetic coupling is due to the
coupling of torsional waves to the conductivity of the
mantle. Whether this is strong enough to account for the
semi-decadal signal is one of the topics discussed in this
talk.
