scholarly journals Numerical Simulations of Penetration and Overshoot in the Sun

2006 ◽  
Vol 653 (1) ◽  
pp. 765-773 ◽  
Author(s):  
Tamara M. Rogers ◽  
Gary A. Glatzmaier ◽  
C. A. Jones
Keyword(s):  
Numerical Simulations ◽  
The Sun

scholarly journals Energetics of magnetic transients in a solar active region plage

2019 ◽  
Vol 623 ◽  
pp. A176 ◽  
Author(s):  
L. P. Chitta ◽  
A. R. C. Sukarmadji ◽  
L. Rouppe van der Voort ◽  
H. Peter
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Magnetic Flux ◽  
Numerical Simulations ◽  
Extreme Ultraviolet ◽  
Spatial Scales ◽  
Coronal Loops ◽  
The Sun ◽  
Flux Emergence ◽  
Transient Events

Context. Densely packed coronal loops are rooted in photospheric plages in the vicinity of active regions on the Sun. The photospheric magnetic features underlying these plage areas are patches of mostly unidirectional magnetic field extending several arcsec on the solar surface. Aims. We aim to explore the transient nature of the magnetic field, its mixed-polarity characteristics, and the associated energetics in the active region plage using high spatial resolution observations and numerical simulations. Methods. We used photospheric Fe I 6173 Å spectropolarimetric observations of a decaying active region obtained from the Swedish 1-m Solar Telescope (SST). These data were inverted to retrieve the photospheric magnetic field underlying the plage as identified in the extreme-ultraviolet emission maps obtained from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). To obtain better insight into the evolution of extended unidirectional magnetic field patches on the Sun, we performed 3D radiation magnetohydrodynamic simulations of magnetoconvection using the MURaM code. Results. The observations show transient magnetic flux emergence and cancellation events within the extended predominantly unipolar patch on timescales of a few 100 s and on spatial scales comparable to granules. These transient events occur at the footpoints of active region plage loops. In one case the coronal response at the footpoints of these loops is clearly associated with the underlying transient. The numerical simulations also reveal similar magnetic flux emergence and cancellation events that extend to even smaller spatial and temporal scales. Individual simulated transient events transfer an energy flux in excess of 1 MW m−2 through the photosphere. Conclusions. We suggest that the magnetic transients could play an important role in the energetics of active region plage. Both in observations and simulations, the opposite-polarity magnetic field brought up by transient flux emergence cancels with the surrounding plage field. Magnetic reconnection associated with such transient events likely conduits magnetic energy to power the overlying chromosphere and coronal loops.

scholarly journals Searching for Orbits with Minimum Fuel Consumption for Station-Keeping Maneuvers: An Application to Lunisolar Perturbations

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Antonio Fernando Bertachini de Almeida Prado
Keyword(s):  
Numerical Simulations ◽  
Fuel Consumption ◽  
Total Variation ◽  
The Sun ◽  
The Moon ◽  
Station Keeping ◽  
Third Body ◽  
Lunisolar Perturbations ◽  
The Earth ◽  
New Criterion

The present paper has the goal of developing a new criterion to search for orbits that minimize the fuel consumption for station-keeping maneuvers. This approach is based on the integral over the time of the perturbing forces. This integral measures the total variation of velocity caused by the perturbations in the spacecraft, which corresponds to the equivalent variation of velocity that an engine should deliver to the spacecraft to compensate the perturbations and to keep its orbit Keplerian all the time. This integral is a characteristic of the orbit and the set of perturbations considered and does not depend on the type of engine used. In this sense, this integral can be seen as a criterion to select the orbit of the spacecraft. When this value becomes larger, more consumption of fuel is required for the station keeping, and, in this sense, less interesting is the orbit. This concept can be applied to any perturbation. In the present research, as an example, the perturbation caused by a third body is considered. Then, numerical simulations considering the effects of the Sun and the Moon in a satellite around the Earth are shown to exemplify the method.

Dynamical Response of the Solar Corona. II. Numerical Simulations Near the Sun

1976 ◽  
Vol 207 ◽  
pp. 300 ◽  
Author(s):  
Richard S. Steinolfson ◽  
Yoshinari Nakagawa
Keyword(s):  
Solar Corona ◽  
Numerical Simulations ◽  
Dynamical Response ◽  
The Sun

Chaos in Robert Hooke's inverted cone

2007 ◽  
Vol 463 (2081) ◽  
pp. 1259-1269 ◽  
Author(s):  
Médéric Argentina ◽  
Pierre Coullet ◽  
Jean-Marc Gilli ◽  
Marc Monticelli ◽  
Germain Rousseaux
Keyword(s):  
Dynamical Systems ◽  
Numerical Simulations ◽  
Gravity Field ◽  
Chaos Theory ◽  
Mechanical Model ◽  
Period Doubling ◽  
The Sun ◽  
Chaotic Motions ◽  
Robert Hooke ◽  
Classical Experiment

Robert Hooke is perhaps one of the first scientists to have met chaotic motions. Indeed, to invert a cone and let a ball move in it was a mechanical model used by him to mimic the motion of a planet around a centre of force like the Sun. However, as the cone is inclined with respect to the gravity field, the perfect rosace followed by the particle becomes chaotic meanderings. We revisit this classical experiment designed by Hooke with the modern tools of dynamical systems and chaos theory. By a combination of both numerical simulations and experiments, we prove that the scenario of transition to the chaotic behaviour is through a period-doubling instability.

Study of starspots in fully convective stars using three dimensional MHD simulations

2018 ◽  
Vol 13 (S340) ◽  
pp. 303-304
Author(s):  
Arnab Basak ◽  
Dibyendu Nandy
Keyword(s):  
High Resolution ◽  
Numerical Simulations ◽  
High Latitude ◽  
Three Dimensional ◽  
Stellar Dynamics ◽  
The Sun ◽  
Dynamo Action ◽  
Magnetic Structures ◽  
Mhd Simulations ◽  
Self Consistent

AbstractConcentrated magnetic structures such as sunspots and starspots play a fundamental role in driving solar and stellar activity. However, as opposed to the sun, observations as well as numerical simulations have shown that stellar spots are usually formed as high-latitude patches extended over wide areas. Using a fully spectral magnetohydrodynamic (MHD) code, we simulate polar starspots produced by self-consistent dynamo action in rapidly rotating convective shells. We carry out high resolution simulations and investigate various properties related to stellar dynamics which lead to starspot formation.

scholarly journals The Puzzling Dynamos of Stars: Recent Progress With Global Numerical Simulations

2016 ◽  
Vol 12 (S328) ◽  
pp. 1-11
Author(s):  
Antoine Strugarek ◽  
Patrice Beaudoin ◽  
Paul Charbonneau ◽  
Allan S. Brun
Keyword(s):  
Numerical Simulations ◽  
High Performance ◽  
Large Scale ◽  
Cycle Period ◽  
Turbulent Regime ◽  
The Sun ◽  
Convective Envelope ◽  
Linear Character ◽  
Cyclic Behaviour ◽  
Magnetic Cycles

AbstractThe origin of magnetic cycles in the Sun and other cool stars is one of the great theoretical challenge in stellar astrophysics that still resists our understanding. Ab-initio numerical simulations are today required to explore the extreme turbulent regime in which stars operate and sustain their large-scale, cyclic magnetic field. We report in this work on recent progresses made with high performance numerical simulations of global turbulent convective envelopes. We rapidly review previous prominent results from numerical simulations, and present for the first time a series of turbulent, global simulations producing regular magnetic cycles whose period varies systematically with the convective envelope parameters (rotation rate, convective luminosity). We find that the fundamentally non-linear character of the dynamo simulated in this work leads the magnetic cycle period to be inversely proportional to the Rossby number. These results promote an original interpretation of stellar magnetic cycles, and could help reconcile the cyclic behaviour of the Sun and other solar-type stars.

scholarly journals Dynamics of small-scale magnetic fields on the Sun: observations and numerical simulations

2008 ◽  
Vol 494 (3) ◽  
pp. 1091-1106 ◽  
Author(s):  
N. Bello González ◽  
L. Yelles Chaouche ◽  
O. Okunev ◽  
F. Kneer
Keyword(s):  
Magnetic Fields ◽  
Numerical Simulations ◽  
Small Scale ◽  
The Sun

scholarly journals Stochastic Excitation in Solar-Type Stars

2002 ◽  
Vol 185 ◽  
pp. 447-455 ◽  
Author(s):  
G. Houdek
Keyword(s):  
Numerical Simulations ◽  
Theoretical Models ◽  
Basic Mechanism ◽  
Convincing Evidence ◽  
Turbulent Convection ◽  
The Sun ◽  
Stochastic Excitation ◽  
Current Belief ◽  
Solar Type

AbstractThe most convincing evidence to date of solar-type oscillations in other stars comes from recent observations of β Hydri (Bedding et al., 2001) and α Cen A (Bouchy & Carrier, 2001). It is the current belief that the convection dynamics in the outer layers of sun-like stars is the source for driving the intrinsically stable modes to the observed amplitudes. Comparing such observations with theoretical models will help us improve our understanding of the interaction between convection and pulsation.In this contribution I review the mechanisms responsible for mode damping in stars with convective envelopes, and the basic mechanism of stochastic driving by turbulent convection. The application of a stochastic excitation formalism to the Sun is discussed and compared with recent measurements and numerical simulations. Amplitude predictions for models of Procyon, α Cen A and β Hydri are compared with observations.

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