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The classic Weber-Davis model of the solar wind is reconsidered by incorporating alpha particles and by allowing the solar wind to flow out of the equatorial plane in an axisymmetrical configuration. In the ion momentum equations of the…

天体物理学 · 物理学 2007-05-23 Bo Li , Xing Li

We introduce to the stellar physics community a method of modelling stellar coronae that can be considered to be an extension of the potential field. In this approach, the magnetic field is coupled to the background atmosphere. The model is…

太阳与恒星天体物理 · 物理学 2015-12-23 David MacTaggart , Scott Gregory , Thomas Neukirch , Jean-Francois Donati

As a cool star evolves, it loses mass and angular momentum due to magnetized stellar winds which affect its rotational evolution. This change has consequences that range from the alteration of its activity to influences over the atmosphere…

太阳与恒星天体物理 · 物理学 2023-07-26 Judy Chebly , Julián D. Alvarado-Gómez , Katja Poppenhäger , Cecilia Garraffo

Numerical MHD simulations play increasingly important role for understanding mechanisms of stellar magnetism. We present simulations of convection and dynamos in density-stratified rotating spherical fluid shells. We employ a new 3D…

太阳与恒星天体物理 · 物理学 2015-09-03 Radostin D. Simitev , Alexander G. Kosovichev , Friedrich H. Busse

The operation of the solar global dynamo appears to involve many dynamical elements. Self-consistent MHD simulations which realistically incorporate all of these processes are not yet computationally feasible, though some elements can now…

天体物理学 · 物理学 2008-11-26 Allan Sacha Brun , Mark S. Miesch , Juri Toomre

The evolution of angular momentum is a key to our understanding of star formation and stellar evolution. The rotational evolution of solar-mass stars is mostly controlled by magnetic interaction with the circumstellar disc and angular…

天体物理学 · 物理学 2009-11-13 Jochen Eisloeffel , Alexander Scholz

Aims. The goal is to employ a 3D magnetohydrodynamics (MHD) model including spectral synthesis to model the corona in an observed solar active region. This will allow us to judge the merits of the coronal heating mechanism built into the 3D…

太阳与恒星天体物理 · 物理学 2017-09-19 Ph. -A. Bourdin , S. Bingert , H. Peter

In the recent years, global coronal models have experienced an ongoing increase in popularity as tools for forecasting solar weather. Within the domain of up to 21.5Rsun, magnetohydrodynamics (MHD) is used to resolve the coronal structure…

太阳与恒星天体物理 · 物理学 2022-11-30 Michaela Brchnelova , Błażej Kuźma , Barbara Perri , Andrea Lani , Stefaan Poedts

We present results from fully general relativistic (GR), three-dimensional (3D), neutrino-radiation magneto-hydrodynamic (MHD) simulations of stellar core collapse of a 20 M$_\odot$ star with spectral neutrino transport. Our focus is to…

高能天体物理现象 · 物理学 2024-08-05 Shota Shibagaki , Takami Kuroda , Kei Kotake , Tomoya Takiwaki , Tobias Fischer

The dynamo action achieved in the convective cores of main-sequence massive stars is explored here through 3D global simulations of convective core dynamos operating within a young $\Msun{10}$ B-type star, using the anelastic spherical…

太阳与恒星天体物理 · 物理学 2016-10-05 Kyle C. Augustson , Allan Sacha Brun , Juri Toomre

Measurement of the coronal magnetic field is a crucial ingredient in understanding the nature of solar coronal phenomena at all scales. We employed STEREO/COR1 data obtained during a deep minimum of solar activity in February 2008…

太阳与恒星天体物理 · 物理学 2014-05-06 M. Kramar , V. Airapetian , Z. Mikić , J. Davila

Magnetoseismology, a technique of magnetic field diagnostics based on observations of magnetohydrodynamic (MHD) waves, has been widely used to estimate the field strengths of oscillating structures in the solar corona. However, previously…

太阳与恒星天体物理 · 物理学 2020-11-05 Zihao Yang , Hui Tian , Steven Tomczyk , Richard Morton , Xianyong Bai , Tanmoy Samanta , Yajie Chen

Observations of young open clusters have revealed a bimodal distribution of fast and slower rotation rates that has proven difficult to explain with predictive models of spin down that depend on rotation rates alone. The Metastable Dynamo…

太阳与恒星天体物理 · 物理学 2015-06-08 Cecilia Garraffo , Jeremy J. Drake , Ofer Cohen

Observations of the rotation rates of horizontal branch (HB) stars show puzzling systematics. In particular, cooler HB stars often show rapid rotation (with velocities in excess of 10 km/s), while hotter HB stars typically show much smaller…

天体物理学 · 物理学 2009-11-10 Steven D. Kawaler , Shelbi R. Hostler

Observations indicate that magnetic fields in rapidly rotating stars are very strong, on both small and large scales. What is the nature of the resulting corona? Here we seek to shed some light on this question. We use the results of an…

太阳与恒星天体物理 · 物理学 2017-01-04 O. Cohen , R. Yadav , C. Garraffo , S. H. Saar , S. J. Wolk , V. L. Kashyap , J. J. Drake , I. Pillitteri

Stellar dynamos are driven by complex couplings between rotation and turbulent convection, which drive global-scale flows and build and rebuild stellar magnetic fields. When stars like our sun are young, they rotate much more rapidly than…

Observations of sun-like stars rotating faster than our current sun tend to exhibit increased magnetic activity as well as magnetic cycles spanning multiple years. Using global simulations in spherical shells to study the coupling of…

太阳与恒星天体物理 · 物理学 2015-05-20 Nicholas J. Nelson , Benjamin P. Brown , Matthew K. Browning , Allan Sacha Brun , Mark S. Miesch , Juri Toomre

We have numerically demonstrated that simulated cool star coronae naturally form condensations. If the star rotates slowly, with a co-rotation radius greater than the Alfv\'{e}n radius (i.e. $R_{\mathrm{K}} > R_{\mathrm{A}}$), these…

太阳与恒星天体物理 · 物理学 2024-09-12 Simon Daley-Yates , Moira Jardine

We performed the first numerical simulations of magnetorotational instability from a sub-magnetar-class seed magnetic field in core collapse supernovae. As a result of axisymmetric ideal MHD simulations, we found that the magnetic field is…

高能天体物理现象 · 物理学 2015-06-15 Hidetomo Sawai , Shoichi Yamada , Hideyuki Suzuki

It is well-known that the cores of massive stars sustain a stellar dynamo with a complex magnetic field configuration. However, the same cannot be said for the field's strength and geometry at the convective-radiative boundary, which are…

太阳与恒星天体物理 · 物理学 2024-12-16 Rathish P. Ratnasingam , Philipp V. F. Edelmann , Dominic M. Bowman , Tamara M. Rogers