Related papers: Explaining the Observed Relation Between Stellar A…
The introduction of the Rossby number (R$_0$), which incorporates the convective turnover time ($\tau$), in 1984 was a pioneering idea for understanding the correlation between stellar rotation and activity. The convective turnover time,…
Differential rotation is central to a great many mysteries in stars and planets. In Part I we predicted the order of magnitude and scaling of the differential rotation in both hydrodynamic and magnetohydrodynamic convection zones. Our…
We present a brief review of observational results contributing to modern ideas on the evolution of stellar activity. Basic laws, derived for both rotation-age and activity-rotation relationships, allow us to trace how the activity of…
Similar to the solar cycle, the magnetic cycles of other solar-type stars are also variable. How the variability of the stellar cycle changes with the rotation rate or the dynamo number is a valuable information for understanding the…
We further investigate relationships between activity cycle periods in cool stars and rotation to include new cycle data, and explore different parameterizations of the problem. We find that relations between cycle and rotational…
The magnetic fields of solar-type stars are observed to cycle over decadal periods -11 years in the case of the Sun. The fields originate in the turbulent convective layers of stars and have a complex dependency upon stellar rotation rate.…
Precise photometry from the Kepler space telescope allows not only the measurement of rotation in solar-type field stars, but also the determination of reliable masses and ages from asteroseismology. These critical data have recently…
Magnetic field observations of low-mass stars reveal an increase of magnetic activity with increasing rotation rate. The so-called activity-rotation relation is usually attributed to changes in the underlying dynamo processes generating the…
The relation between magnetic activity and rotation in late-type stars provides fundamental information on stellar dynamos and angular momentum evolution. Rotation/activity studies found in the literature suffer from inhomogeneity in the…
The activity of the Sun as a result of cyclic changes of the global magnetic field is studied. As a consequence of the analysis of magnetic activity of solar-type stars the following power dependencies were found: the dependence between the…
We study the relation between stellar rotation and magnetic activity for a sample of 134 bright, nearby M dwarfs observed in the Kepler Two-Wheel (K2) mission during campaigns C0 to C4. The K2 lightcurves yield photometrically derived…
From our sample of spotted late-type stars showing surface differential rotation we find that the relationship between the rotation period and the surface shear coefficient $\alpha=\Delta\Omega/\Omega_{\rm eq}$ is significantly different…
During the first half of main-sequence lifetimes, the evolution of rotation and magnetic activity in solar-type stars appears to be strongly coupled. Recent observations suggest that rotation rates evolve much more slowly beyond middle-age,…
To better understand the observed distributions of rotation rate and magnetic activity of sun-like and low-mass stars, we derive a physically motivated scaling for the dependence of the stellar-wind torque on Rossby number. The torque also…
Low-mass (< 1.2 Solar mass) main-sequence stars lose angular momentum over time, leading to a decrease in their magnetic activity. The details of this rotation-activity relation remain poorly understood. Using observations of members of the…
Stellar surface rotation carries information about stellar parameters---particularly ages---and thus the large rotational datasets extracted from Kepler timeseries represent powerful probes of stellar populations. In this article, we…
We show here that the rotation period data in open clusters allow the empirical determination of an expression for the rate of loss of angular momentum from cool stars on the main sequence. One significant component of the expression, the…
We present the results of a spectroscopic survey to characterize chromospheric activity, as measured by H$\alpha$ emission, in low-mass members of the 500-Myr-old open cluster M37. Combining our new measurements of H$\alpha$ luminosities…
According to dynamo theory, stars with convective envelopes efficiently generate surface magnetic fields, which manifest as magnetic activity in the form of starspots, faculae, flares, when their rotation period is shorter than their…
(abridged) A method for simulating light curves containing stellar micro-variability for a range of spectral types and ages, based on parameter-by-parameter scaling of a multi-component fit to the solar irradiance power spectrum (from…