R. H. Cameron
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View article: Closing the solar dynamo loop: Poloidal field generated at the surface by plasma flows
Closing the solar dynamo loop: Poloidal field generated at the surface by plasma flows Open
Context. The large-scale magnetic field of the Sun is produced by dynamo action due to convection and rotation. The toroidal magnetic field is maintained by the Sun’s differential rotation that winds up the azimuthally averaged radial and …
View article: Probing chromospheric fine structures with a H<i>α</i> proxy using MURaM-ChE
Probing chromospheric fine structures with a H<i>α</i> proxy using MURaM-ChE Open
Context. H α observations of the solar chromosphere reveal dynamic small-scale structures known as spicules at the limb and rapid blueshifted and redshifted excursions (RBEs and RREs) on-disc. Aims. We want to understand what drives these …
View article: Coriolis force acting on near-surface horizontal flows during simulations of flux emergence produces a tilt angle consistent with Joy’s law on the Sun
Coriolis force acting on near-surface horizontal flows during simulations of flux emergence produces a tilt angle consistent with Joy’s law on the Sun Open
Context. Joy’s law describes the tilt of bipolar active regions on the Sun away from an east-west orientation, where the flux of the polarity concentrated at the prograde side tends to be closer to the equator than the polarity on the retr…
View article: Probing Solar Polar Regions
Probing Solar Polar Regions Open
The magnetic fields and dynamical processes in the solar polar regions play a crucial role in the solar magnetic cycle and in supplying mass and energy to the fast solar wind, ultimately being vital in controlling solar activities and driv…
View article: Enhanced magnetic activity in rapidly rotating binary stars
Enhanced magnetic activity in rapidly rotating binary stars Open
Stellar activity is fundamental to stellar evolution and the formation and habitability of exoplanets. The interaction between convective motions and rotation in cool stars results in a dynamo process that drives magnetic surface activity.…
View article: 3D radiative MHD simulations of starspots
3D radiative MHD simulations of starspots Open
We computed realistic 3D radiative magnetohydrodynamic (MHD) near-surface models of starspots with substantial penumbrae on cool main sequence stars using the MURaM simulation code. This work is an improvement on the previous starspot mode…
View article: First Calculations of Starspot Spectra Based on 3D Radiative Magnetohydrodynamics Simulations
First Calculations of Starspot Spectra Based on 3D Radiative Magnetohydrodynamics Simulations Open
Accurate calculations of starspot spectra are essential for multiple applications in astronomy. The current standard is to represent starspot spectra by spectra of stars that are cooler than the quiet star regions. This implies approximati…
View article: Low-latitude Magnetic Flux Emergence on Rapidly Rotating Solar-type Stars
Low-latitude Magnetic Flux Emergence on Rapidly Rotating Solar-type Stars Open
Besides a dense coverage of their high latitudes by starspots, rapidly rotating cool stars also display low-latitude spots in Doppler images, although generally with lower coverage. In contrast, flux emergence models of fast-rotating stars…
View article: The rush to the poles and the role of magnetic buoyancy in the solar dynamo
The rush to the poles and the role of magnetic buoyancy in the solar dynamo Open
Context. The butterfly diagram of the solar cycle shows a poleward migration of the diffuse magnetic field resulting from the decay of trailing sunspots. It is one component of what is sometimes referred to as the ‘rush to the poles’ and i…
View article: The rush to the poles and the role of magnetic buoyancy in the solar dynamo
The rush to the poles and the role of magnetic buoyancy in the solar dynamo Open
The butterfly diagram of the solar cycle exhibits a poleward migration of the diffuse magnetic field resulting from the decay of trailing sunspots. It is one component of what is sometimes referred to as the "rush to the poles". We investi…
View article: Enhanced magnetic activity in rapidly rotating binary stars
Enhanced magnetic activity in rapidly rotating binary stars Open
The interaction between convective motions and rotation in cool stars results in a dynamo process that drives magnetic surface activity1, 2. In single stars, activity increases with rotation rate until it saturates for stars with rotation …
View article: Combined Surface Flux Transport and Helioseismic Far-Side Active Region Model (FARM)
Combined Surface Flux Transport and Helioseismic Far-Side Active Region Model (FARM) Open
Maps of the magnetic field at the Sun’s surface are commonly used as boundary conditions in space-weather modeling. However, continuous observations are only available from the Earth-facing part of the Sun’s surface. One commonly used appr…
View article: Mg II h&k spectra of an enhanced network region simulated with the MURaM-ChE code
Mg II h&k spectra of an enhanced network region simulated with the MURaM-ChE code Open
Context. The Mg II h&k lines are key diagnostics of the solar chromosphere. They are sensitive to the temperature, density, and nonthermal velocities in the chromosphere. The average Mg II h&k line profiles arising from previous 3D chromos…
View article: Low-latitude magnetic flux emergence on rapidly rotating solar-type stars
Low-latitude magnetic flux emergence on rapidly rotating solar-type stars Open
Besides a dense coverage of their high latitudes by starspots, rapidly rotating cool stars also display low-latitude spots in Doppler images, although generally with a lower coverage. In contrast, flux emergence models of fast-rotating sta…
View article: Mg ii h&k spectra of an enhanced network region simulated with the MURaM-ChE code. Results using 1.5D synthesis
Mg ii h&k spectra of an enhanced network region simulated with the MURaM-ChE code. Results using 1.5D synthesis Open
The Mg ii h&k lines are key diagnostics of the solar chromosphere. They are sensitive to the temperature, density, and non-thermal velocities in the chromosphere. The average Mg ii h&k line profiles arising from previous 3D chromospheric s…
View article: The mean solar butterfly diagram and poloidal field generation rate at the surface of the Sun
The mean solar butterfly diagram and poloidal field generation rate at the surface of the Sun Open
Context. The difference between individual solar cycles in the magnetic butterfly diagram can mostly be ascribed to the stochasticity of the emergence process. Aims. We aim to obtain the expectation value of the butterfly diagram from obse…
View article: Solar Inertial Modes
Solar Inertial Modes Open
The Sun's global inertial modes are very sensitive to the solar differential rotation and to properties of the deep solar convection zone which are currently poorly constrained. These properties include the superadiabatic temperature gradi…
View article: A flux-independent increase in outflows prior to the emergence of active regions on the Sun
A flux-independent increase in outflows prior to the emergence of active regions on the Sun Open
Emerging active regions are associated with convective flows on the spatial scale and lifetimes of supergranules. To understand how these flows are involved in the formation of active regions, we aim to identify where active regions emerge…
View article: A flux-independent increase in outflows prior to the emergence of active regions on the Sun
A flux-independent increase in outflows prior to the emergence of active regions on the Sun Open
Emerging active regions are associated with convective flows on the spatial scale and lifetimes of supergranules. To understand how these flows are involved in the formation of active regions, we aim to identify where active regions emerge…
View article: The mean solar butterfly diagram and poloidal field generation rate at the surface of the Sun
The mean solar butterfly diagram and poloidal field generation rate at the surface of the Sun Open
The difference between individual solar cycles in the magnetic butterfly diagram can mostly be ascribed to the stochasticity of the emergence process. We aim to obtain the expectation value of the butterfly diagram from observations of fou…
View article: Magnetic origin of the discrepancy between stellar limb-darkening models and observations
Magnetic origin of the discrepancy between stellar limb-darkening models and observations Open
Stars appear darker at their limbs than at their disk centres because at the limb we are viewing the higher and cooler layers of stellar photospheres. Yet, limb darkening derived from state-of-the-art stellar atmosphere models systematical…
View article: The Sun’s differential rotation is controlled by high-latitude baroclinically unstable inertial modes
The Sun’s differential rotation is controlled by high-latitude baroclinically unstable inertial modes Open
Rapidly rotating fluids have a rotation profile that depends only on the distance from the rotation axis, in accordance with the Taylor-Proudman theorem. Although the Sun was expected to be such a body, helioseismology showed that the rota…
View article: Stellar Surface Magnetic Fields Impact Limb Darkening
Stellar Surface Magnetic Fields Impact Limb Darkening Open
Stars appear darker at their limbs than at their disk centers because at the limb we are viewing the higher and cooler layers of stellar photospheres. Limb darkening derived from state-of-the-art stellar atmosphere models systematically fa…
View article: How well does surface magnetism represent deep Sun-like star dynamo action?
How well does surface magnetism represent deep Sun-like star dynamo action? Open
Context. For Sun-like stars, the generation of toroidal magnetic field from poloidal magnetic field is an essential piece of the dynamo mechanism powering their magnetism. Previous authors have estimated the net toroidal flux generated in …
View article: How well does surface magnetism represent deep Sun-like star dynamo action?
How well does surface magnetism represent deep Sun-like star dynamo action? Open
For Sun-like stars, the generation of toroidal magnetic field from poloidal magnetic field is an essential piece of the dynamo mechanism powering their magnetism. Previous authors have estimated the net toroidal flux generated in each hemi…
View article: Editorial to the Topical Collection: Solar and Stellar Dynamos: a New Era
Editorial to the Topical Collection: Solar and Stellar Dynamos: a New Era Open
Large-scale and small-scale dynamos generating magnetic flux are fundamental processes in astrophysics, for which solar and stellar dynamos provide crucial paradigms.During the last two decades, a wealth of new observational results, toget…
View article: The influence of small bipolar magnetic regions on basic solar quantities
The influence of small bipolar magnetic regions on basic solar quantities Open
Context. Understanding the evolution of the solar magnetic field is of great importance for heliosphere, dynamo, and irradiance studies, for example. While the contribution of the field in active regions (ARs) hosting sunspots to the Sun’s…
View article: Solar Inertial Modes
Solar Inertial Modes Open
The Sun’s global inertial modes are very sensitive to the solar differential rotation and to properties of the deep solar convection zone which are currently poorly constrained. These properties include the superadiabatic temperature gradi…
View article: Small-scale dynamo in cool stars
Small-scale dynamo in cool stars Open
Context. Some of the quiet solar magnetic flux could be attributed to a small-scale dynamo (SSD) operating in the convection zone. An SSD operating in cool main-sequence stars is expected to affect the atmospheric structure, in particular,…