Скачать или смотреть Prof. Christopher Jones | Some reflections on the scientific life of Paul Roberts

Speaker(s) Christopher Jones University of Leeds
Date 1 December 2022 – 09:45 to 10:00
Venue INI Seminar Room 1
Session Title Some reflections on the scientific life of Paul Roberts
Event [DY2W03] Modeling, observing and understanding flows and magnetic fields in the Earth's core and in the Sun
Abstract
Convective motions which develop in the Earth liquid outer core or in the deep
interior of the gas giants planets are thought to be the main driver of
planetary magnetic fields via dynamo action. These electrically-conducting
fluid regions are nevertheless not necessarily entirely convecting.

In the case of the Earth core, corroborating evidences coming from seismic
studies, mineral physics and thermal evolution models suggest the existence of
a stably-stratified layer underneath the core–mantle boundary. Such a layer
could find its physical origination either in compositional stratification due
to the accumulation of light elements at the top or the core or in thermal
stratification due to the heat flux becoming locally sub-adiabatic. In the case
of gas giant planets, constraints coming from gravity measurements, ab-initio
calculations and ring-seismology (in the case of Saturn) suggest an intricate
internal structure with fluid regions where helium would segregate from
hydrogen, forming a compositionally-stratified layer.

Such stable layers can have crucial dynamical impacts on dynamo action. Because
of the inhibition of the convective motions, a stable layer is expected to
primarily act as a low-pass filter on the magnetic field, smoothing out the
rapidly-varying and small-scale features by skin effect. This defines a
magnetic constraint on the properties of stably-stratified layers in planetary
interiors.

During this talk, I will present global numerical dynamo models of the
geodynamo and of the gas giants planets which incorporate stably-stratified
layers to quantify their impact on the magnetic field generation.