Related papers: Solar and stellar activity cycles -- no synchroniz…
Energetic particles, such as stellar cosmic rays, produced at a heightened rate by active stars (like the young Sun) may have been important for the origin of life on Earth and other exoplanets. Here we compare, as a function of stellar…
We observe the abrupt end of solar activity cycles at the Sun's equator by combining almost 140 years of observations from ground and space. These "terminator" events appear to be very closely related to the onset of magnetic activity…
Observations of the Sun and of Sun-like stars provide access to different aspects of stellar magnetic activity that, when combined, help us piece together a more comprehensive picture than can be achieved from only the solar or the stellar…
Magnetic fields play an important role at all stages of stellar evolution. In Sun-like stars, they are generated in the outer convective layers. Studying the large-scale magnetic fields of these stars enlightens our understanding of the…
An update is given on the current status of solar and stellar dynamos. At present, it is still unclear why stellar cycle frequencies increase with rotation frequency in such a way that their ratio increases with stellar activity. The…
The magnetic activity of the Sun becomes stronger and weaker over roughly an 11 year cycle, modulating the radiation and charged particle environment experienced by the Earth as "space weather". Decades of observations from the Mount Wilson…
Five new correlations between sunspot activity and orbiting position of the Jovian planets are detected. In order to explain these correlations it is suggested that the resonance of the outer planets destabilizes the orbit of Kuiper Belt…
One of the most striking manifestations of orderly behavior emerging out of complex interactions in any astrophysical system is the 11-year cycle of sunspots. However, direct sunspot observations and reconstructions of long-term solar…
Planets interact with their host stars through gravity, radiation and magnetic fields, and for those giant planets that orbit their stars within ~10 stellar radii (~0.1 AU for a sun-like star), star-planet interactions (SPI) are observable…
M-dwarfs demonstrate two types of activity: 1) strong (kilogauss) almost axisymmetric poloidal magnetic fields; and 2) considerably weaker nonaxisymmetric fields, sometimes including a substantial toroidal component. Dynamo bistability has…
Through the process of thermal ionization, intense stellar irradiation renders Hot Jupiter atmospheres electrically conductive. Simultaneously, lateral variability in the irradiation drives the global circulation with peak wind speeds of…
The evolution of a star is influenced by its internal rotation dynamics through transport and mixing mechanisms, which are poorly understood. Magnetic fields can play a role in transporting angular momentum and chemical elements, but the…
We further develop the Tayler--Spruit dynamo theory, based on the most efficient instability for generating magnetic fields in radiative layers of differentially rotating stars. We avoid the simplifying assumptions that either the $\mu$--…
Planets close to their host stars are believed to undergo significant tidal interactions, leading to a progressive damping of the orbital eccentricity. Here we show that, when the orbit of the planet is excited by an outer companion, tidal…
In the coming decades, the discovery of the first truly Earth-like exoplanets is anticipated. The characterisation of those planets will play a vital role in determining which are chosen as targets for the search for life beyond the Solar…
The Sun is forced into an orbit around the barycenter of the solar system because of the changing mass distribution of the planets. Solar-planetary-lunar dynamic relationships may form a new basis for understanding and predicting cyclic…
Observations of the meridional circulation of the Sun, which plays a key role in the operation of the solar dynamo, indicate that its speed varies with the solar cycle, becoming faster during the solar minima and slower during the solar…
Magnetic fields generated in the Sun's interior by the solar dynamo mechanism drive solar activity over a range of time-scales. While space-based observations of the Sun's corona exist only for few decades, direct sunspot observations exist…
The details of the dynamo process that is responsible for driving the solar magnetic activity cycle are still not fully understood. In particular, whilst differential rotation provides a plausible mechanism for the regeneration of the…
The evolution of the solar activity comprises, apart from the well-known 11-year cycle, various temporal scales ranging from months up to the secondary cycles known as mid-term oscillations. Its nature deserves a physical explanation. In…