6 papers · 1 filter
Surface distribution of small-scale magnetic field on the active cool star LQ Hydrae
O. Kochukhov, T. Hackman, J. J. Lehtinen
It is well known that small-scale magnetism dominates the surface magnetic field topologies of active late-type stars. However, little information is available on the spatial distr…
Zeeman-Doppler imaging of five young solar-type stars
T. Willamo, J. J. Lehtinen, T. Hackman +5
The magnetic activity of the Sun changes with the solar cycle. Similar cycles are found in other stars as well, but their details are not known to a similar degree. Characterising…
Shapes of stellar activity cycles
T. Willamo, T. Hackman, J. J. Lehtinen +4
Magnetic activity cycles are an important phenomenon in both the Sun and other stars. The shape of the solar cycle is commonly characterised by a fast rise and a slower decline, bu…
Estimating activity cycles with probabilistic methods II. The Mount Wilson Ca H&K data
N. Olspert, J. Lehtinen, M. J. Käpylä +2
Debate over the existence of branches in the stellar activity-rotation diagrams continues. Application of modern time series analysis tools to study the mean cycle periods in chrom…
Estimating activity cycles with probabilistic methods I. Bayesian Generalised Lomb-Scargle Periodogram with Trend
N. Olspert, J. Pelt, M. J. Käpylä +1
Period estimation is one of the central topics in astronomical time series analysis, where data is often unevenly sampled. Especially challenging are studies of stellar magnetic cy…
Transition from axi- to nonaxisymmetric dynamo modes in spherical convection models of solar-like stars
Mariangela Viviani, Jörn Warnecke, Maarit J. Käpylä +5
We seek to understand the transition from nearly axisymmetric configurations at solar rotation rates to nonaxisymmetric configurations for rapid rotation using 3D numerical simulat…