Petri Käpylä (AIP)

Cracking the convective conundrum
When Sep 22, 2016 from 02:30 PM to 03:30 PM
What
  • Colloquium
Where SH Lecture Hall
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Convection plays a crucial role in many processes in stellar physics:  it is responsible for generating differential rotation and it is  thought to facilitate the growth of stellar magnetic fields via a turbulent dynamo. Convection also mixes the stellar matter efficiently  which is important in many phases of stellar evolution.

Current stellar models rely on mixing length models which predict a convection zone depth of 200Mm in the the Sun coinciding with helioseismic constraints. This implies that the largest convective scale, or so-called giant cells, should be excited at that scale. Recent helioseismic results, however, suggest very weak amplitudes for velocities at large scales. Furthermore, three-dimensional numerical simulations of stellar convection yield much higher velocities and struggle to reproduce observed large-scale effects such as solar differential rotation. This discrepancy between  observations and theory has been dubbed the `convective conundrum.'

This issue suggests that either the theory of stellar convection is fundamentally flawed or that the current simulations of stellar convection are too unrealistic or too far removed from stellar parameter regimes to be of practical use. However, all of these aspects are likely to be closely intertwined and that the solution requires improvements in all of them. The aim of the talk is to review current developments in stellar convection theory that can crack the convective conundrum.