Solar Photosphere: Center-to-limb Variation

2004 ◽  
Author(s):  
Heinz Neckel
Keyword(s):  
Solar Photosphere

Turbulent convective flows in the solar photospheric plasma

2015 ◽  
Vol 81 (5) ◽  
Author(s):  
A. Caroli ◽  
F. Giannattasio ◽  
M. Fanfoni ◽  
D. Del Moro ◽  
G. Consolini ◽  
...  
Keyword(s):  
Mean Square Displacement ◽  
Small Scale ◽  
Solar Photosphere ◽  
Distribution Analysis ◽  
Pixel Resolution ◽  
Convective Flows ◽  
Magnetic Elements ◽  
Highly Nonlinear ◽  
Convective Motions ◽  
Short Time

The origin of the 22-year solar magnetic cycle lies below the photosphere where multiscale plasma motions, due to turbulent convection, produce magnetic fields. The most powerful intensity and velocity signals are associated with convection cells, called granules, with a scale of typically 1 Mm and a lifetime of a few minutes. Small-scale magnetic elements (SMEs), ubiquitous on the solar photosphere, are passively transported by associated plasma flows. This advection makes their traces very suitable for defining the convective regime of the photosphere. Therefore the solar photosphere offers an exceptional opportunity to investigate convective motions, associated with compressible, stratified, magnetic, rotating and large Rayleigh number stellar plasmas. The magnetograms used here come from a Hinode/SOT uninterrupted 25-hour sequence of spectropolarimetric images. The mean-square displacement of SMEs has been modelled with a power law with spectral index ${\it\gamma}$. We found ${\it\gamma}=1.34\pm 0.02$ for times up to ${\sim}2000~\text{s}$ and ${\it\gamma}=1.20\pm 0.05$ for times up to ${\sim}10\,000~\text{s}$. An alternative way to investigate the advective–diffusive motion of SMEs is to look at the evolution of the two-dimensional probability distribution function (PDF) for the displacements. Although at very short time scales the PDFs are affected by pixel resolution, for times shorter than ${\sim}2000~\text{s}$ the PDFs seem to broaden symmetrically with time. In contrast, at longer times a multi-peaked feature of the PDFs emerges, which suggests the non-trivial nature of the diffusion–advection process of magnetic elements. A Voronoi distribution analysis shows that the observed small-scale distribution of SMEs involves the complex details of highly nonlinear small-scale interactions of turbulent convective flows detected in solar photospheric plasma.

Comments on the reconnexion rate of magnetic fields

1973 ◽  
Vol 9 (1) ◽  
pp. 49-63 ◽  
Author(s):  
E. N. Parker
Keyword(s):  
Velocity Field ◽  
Magnetic Fields ◽  
Turbulent Flows ◽  
Similarity Solutions ◽  
Neutral Point ◽  
Solar Photosphere ◽  
Complete Field ◽  
Fluid Equations ◽  
The Galaxy

The reconnexion rate of magnetic fields is crucial in understanding the fields found in turbulent flows in the solar photosphere and in the galaxy, and in flare phenomena. This paper examines the behaviour of magnetic fields in the neighbourhood of an X-type neutral point. The treatment is kinematical, specifying the velocity field v and constructing solutions to the hydromagnetic equation for B. The calculations demonstrate that the reconnexion rate is controlled by the diffusion in the near neighbourhood of the neutral point, and is not arbitrarily large, as has been suggested by similarity solutions of the complete field and fluid equations for vanishing diffusion

On the structure and energetics of large scale hydromagnetic disturbances in the solar photosphere

Tellus ◽  
1965 ◽  
Vol 17 (3) ◽  
pp. 334-340 ◽  
Author(s):  
Victor P. Starr ◽  
Peter A. Gilman
Keyword(s):  
Large Scale ◽  
Solar Photosphere

scholarly journals MHDSTS: a new explicit numerical scheme for simulations of partially ionised solar plasma

2018 ◽  
Vol 615 ◽  
pp. A67 ◽  
Author(s):  
P. A. González-Morales ◽  
E. Khomenko ◽  
T. P. Downes ◽  
A. de Vicente
Keyword(s):  
Numerical Scheme ◽  
Operator Splitting ◽  
Conservation Equation ◽  
Ambipolar Diffusion ◽  
Point Of View ◽  
Integration Time ◽  
Solar Photosphere ◽  
Time Step ◽  
Diffusion Term ◽  
Fluid Approximation

The interaction of plasma with magnetic field in the partially ionised solar atmosphere is frequently modelled via a single-fluid approximation, which is valid for the case of a strongly coupled collisional media, such as solar photosphere and low chromosphere. Under the single-fluid formalism the main non-ideal effects are described by a series of extra terms in the generalised induction equation and in the energy conservation equation. These effects are: Ohmic diffusion, ambipolar diffusion, the Hall effect, and the Biermann battery effect. From the point of view of the numerical solution of the single-fluid equations, when ambipolar diffusion or Hall effects dominate can introduce severe restrictions on the integration time step and can compromise the stability of the numerical scheme. In this paper we introduce two numerical schemes to overcome those limitations. The first of them is known as super time-stepping (STS) and it is designed to overcome the limitations imposed when the ambipolar diffusion term is dominant. The second scheme is called the Hall diffusion scheme (HDS) and it is used when the Hall term becomes dominant. These two numerical techniques can be used together by applying Strang operator splitting. This paper describes the implementation of the STS and HDS schemes in the single-fluid code MANCHA3D. The validation for each of these schemes is provided by comparing the analytical solution with the numerical one for a suite of numerical tests.

scholarly journals An Updated Line List for NUV Spectral Synthesis in Evolved Stars: Redetermination of the Beryllium Abundance in the Solar Photosphere

2018 ◽  
Vol 865 (1) ◽  
pp. 8 ◽  
Author(s):  
Joleen K. Carlberg ◽  
Katia Cunha ◽  
Verne V. Smith ◽  
José-Dias do Nascimento
Keyword(s):  
Spectral Synthesis ◽  
Solar Photosphere ◽  
Line List ◽  
Evolved Stars

scholarly journals High-Resolution Observations of Emerging Magnetic Fields and Flux Tubes in Active Region Photosphere

1990 ◽  
Vol 138 ◽  
pp. 147-152 ◽  
Author(s):  
T. Tarbell ◽  
S. Ferguson ◽  
Z. Frank ◽  
R. Shine ◽  
A. Title ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Solar Observatory ◽  
Disk Center ◽  
Line Center ◽  
Solar Photosphere ◽  
Flux Tubes ◽  
National Solar Observatory ◽  
La Palma ◽  
The Relationship

On 29 September 1988, filtergrams of the solar photosphere with excellent resolution (0.3 to 0.5 arcsecond) were obtained at the Swedish Solar Observatory on La Palma, Canary Islands. An outstanding 2.5 hour run of digital filtergram observations was obtained, looking at a small area within an active region near disk center. On 6 August 1987, an 80 minute run of similar observations was obtained at the Vacuum Tower Telescope of the National Solar Observatory at Sacramento Peak. Digital and video movies have been made of Dopplergrams, magnetograms, line center, continuum, and white light images. Several examples of magnetic field emergence and formation of flux tubes can be studied in detail in the movies. The relationship between photospheric bright points, “filigree”, the line center brightness, and the magnetic field has been established for individual images in analysis to date.

scholarly journals The Nature of Microturbulence in the Solar Photosphere

1974 ◽  
Vol 166 (1) ◽  
pp. 219-233 ◽  
Author(s):  
A. M. Wilson ◽  
F. J. Guidry
Keyword(s):  
Solar Photosphere
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