10:00 〜 10:15
[SEM15-05] Geomagnetic field generation mechanisms driven by outer core convection with a stably stratified layer
キーワード：stable stratified layer, core convection, dynamo action, geomagnetic field, vortex flows
The possibility of a stable stratified layer near CMB has significant effects on dynamics of
the Earth's outer core as well as the geomagnetic field. In this study, we investigate the
effect of thermally stable stratification by incorporating a radially varying source in a
spherical shell outer core fluid model. From the study of extensive parameter regimes of
different rotation rates and material properties, the evolution of axial vorticity is invetigated.
This has shown the role of vorticity distribution asymmetry which is one of the main
responsible quantities of generating magnetic fields and sustaining dynamo action. We
have investigated the thickness of stable stratified layers ranging from 200 km -700 km
with varying intensities and boundary heat flux. Our aim is to study the dynamics of the
outer core related to the generation of magnetic fields in strongly driven convection. With
increase of stratification thickness, total axial vorticity will decrease and most significantly
its peak will be shifted towards the inner core; no such kind of concentration of vorticity
can be found for the case of unstratified outer core. The difference in vorticity, in presence
and in absence of magnetic field, will provide the idea about how strong the magnetic
field can be. The difference in anticyclonic and cyclonic vorticity in absence of magnetic
field will decide the sustainability of dynamo action. This separation will become less
prominent in presence of strong stratification near CMB. The anticyclonic vorticity is always
dominant over the cyclonic one but the cyclonic vorticity is more able to penetrate the
stratification than the anticyclonic vorticity.
the Earth's outer core as well as the geomagnetic field. In this study, we investigate the
effect of thermally stable stratification by incorporating a radially varying source in a
spherical shell outer core fluid model. From the study of extensive parameter regimes of
different rotation rates and material properties, the evolution of axial vorticity is invetigated.
This has shown the role of vorticity distribution asymmetry which is one of the main
responsible quantities of generating magnetic fields and sustaining dynamo action. We
have investigated the thickness of stable stratified layers ranging from 200 km -700 km
with varying intensities and boundary heat flux. Our aim is to study the dynamics of the
outer core related to the generation of magnetic fields in strongly driven convection. With
increase of stratification thickness, total axial vorticity will decrease and most significantly
its peak will be shifted towards the inner core; no such kind of concentration of vorticity
can be found for the case of unstratified outer core. The difference in vorticity, in presence
and in absence of magnetic field, will provide the idea about how strong the magnetic
field can be. The difference in anticyclonic and cyclonic vorticity in absence of magnetic
field will decide the sustainability of dynamo action. This separation will become less
prominent in presence of strong stratification near CMB. The anticyclonic vorticity is always
dominant over the cyclonic one but the cyclonic vorticity is more able to penetrate the
stratification than the anticyclonic vorticity.