COLLOQUIUM Petri Käpylä (Institute for Solar Physics KIS)

Intermittency and fluctuations in near-critical convection-driven dynamos

The Sun has an 11-year activity cycle that manifests itself as increasing and decreasing occurrence of sunspots on its surface. The directly observed sunspot record spans from the early 17th century until today. The strength of the solar cycle changes from cycle to cycle and direct observations cover a remarkable period, the Maunder Minimum, between around 1645-1715 during which very few sunspot were observed. Cosmogenic isotopes from ice cores and tree rings have revealed several such episodes, referred to as Grand Minima, in the past ten thousand years. A possible explanation for this is that the solar dynamo is only very mildly supercritical and that a relatively small fluctuation in the dynamo parameters can nudge it into an extended minimum. I present results from near-critical 3D convection-driven dynamo simulations that exhibit grand minima and high levels of intermittency and fluctuations, and summarize the implications of these results for the Sun and other stars.

Talk via Zoom:

https://uni-hamburg.zoom.us/j/66006535328?pwd=aGkrSjJIYmZjK0VpYlpGL0ZrdHg2UT09