30 citations · 246 across the 15 of their papers we have counts for
11 papers · 1 filter
Inferring magnetic helicity spectrum in spherical domains: the method and example applications
A. P. Prabhu, N. K. Singh, M. J. Käpylä +1
Obtaining observational constraints on the role of turbulent effects for the solar dynamo is a difficult, yet crucial, task. Without such knowledge, the full picture of the operati…
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…
Topological changes in the magnetic field of LQ Hya during an activity minimum
Jyri J. Lehtinen, Maarit J. Käpylä, Thomas Hackman +6
Previous studies have related surface temperature maps, obtained with the Doppler imaging (DI) technique, of LQ Hya with long-term photometry. We compare surface magnetic field map…
Differences in the solar cycle variability of simple and complex active regions during 1996-2018
Shabnam Nikbakhsh, Eija Tanskanen, Maarit Käpylä +1
Aims. Our aim is to examine the solar cycle variability of magnetically simple and complex active region. Methods. We studied simple ( and ) and complex ( and ) acti…
Stellar dynamos in the transition regime: multiple dynamo modes and anti-solar differential rotation
M. Viviani, M. J. Käpylä, J. Warnecke +2
Global and semi-global convective dynamo simulations of solar-like stars are known to show a transition from an anti-solar (fast poles, slow equator) to solar-like (fast equator, s…
Starspot activity of HD 199178. Doppler images from 1994--2017
Thomas Hackman, Iya Ilyin, Jyri J. Lehtinen +4
Context. Studying the spots of late-type stars is crucial for distinguishing between the various proposed dynamo mechanisms believed to be the main cause of starspot activity. For…
Effects of a subadiabatic layer on convection and dynamos in spherical wedge simulations
Petri J. Käpylä, Mariangela Viviani, Maarit J. Käpylä +2
We consider the effect of a subadiabatic layer at the base of the convection zone on convection itself and the associated large-scale dynamos in spherical wedge geometry. We use a…
Small-scale dynamos in simulations of stratified turbulent convection
Petri J. Käpylä, Maarit J. Käpylä, Axel Brandenburg
Small-scale dynamo action is often held responsible for the generation of quiet-Sun magnetic fields. We aim to determine the excitation conditions and saturation level of small-sca…
Long-term variations of turbulent transport coefficients in a solar-like convective dynamo simulation
Frederick A. Gent, Maarit J. Käpylä, Jörn Warnecke
The Sun, aside from its eleven year sunspot cycle is additionally subject to long term variation in its activity. In this work we analyse a solar-like convective dynamo simulation,…
Method of frequency dependent correlations: investigating the variability of total solar irradiance
Jaan Pelt, Maarit Käpylä, Nigul Olspert
This paper contributes to the field of modeling and hindcasting of the total solar irradiance (TSI) based on different proxy data that extend further back in time than the TSI that…
Zeeman-Doppler imaging of active young solar type stars
Thomas Hackman, Jyri Lehtinen, Lisa Rosén +2
By studying young magnetically active late-type stars, i.e. analogues to the young Sun, one can draw conclusions on the evolution of the solar dynamo. We determine the topology of…