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On the Surface Waves in the Solar Photosphere  [PDF]
M. B. Kerimbekov
Physics , 2001,
Abstract: The regular structures similar to the chains and clusters on the Solar Photosphere are investigated and mechanism these origin are proposed.
MHD simulations of the solar photosphere  [PDF]
M. Rieutord,F. Rincon,T. Roudier
Physics , 2012, DOI: 10.1051/eas/1255001
Abstract: We briefly review the observations of the solar photosphere and pinpoint some open questions related to the magnetohydrodynamics of this layer of the Sun. We then discuss the current modelling efforts, addressing among other problems, that of the origin of supergranulation.
Vorticity in the solar photosphere  [PDF]
S. Shelyag,P. Keys,M. Mathioudakis,F. P. Keenan
Physics , 2010, DOI: 10.1051/0004-6361/201015645
Abstract: Aims. We use magnetic and non-magnetic 3D numerical simulations of solar granulation and G-band radiative diagnostics from the resulting models to analyse the generation of small-scale vortex motions in the solar photosphere. Methods. Radiative MHD simulations of magnetoconvection are used to produce photospheric models. Our starting point is a non-magnetic model of solar convection, where we introduce a uniform magnetic field and follow the evolution of the field in the simulated photosphere. We find two different types of photospheric vortices, and provide a link between the vorticity generation and the presence of the intergranular magnetic field. A detailed analysis of the vorticity equation, combined with the G-band radiative diagnostics, allows us to identify the sources and observational signatures of photospheric vorticity in the simulated photosphere. Results. Two different types of photospheric vorticity, magnetic and non-magnetic, are generated in the domain. Nonmagnetic vortices are generated by the baroclinic motions of the plasma in the photosphere, while magnetic vortices are produced by the magnetic tension in the intergranular magnetic flux concentrations. The two types of vortices have different shapes. We find that the vorticity is generated more efficiently in the magnetised model. Simulated G-band images show a direct connection between magnetic vortices and rotary motions of photospheric bright points, and suggest that there may be a connection between the magnetic bright point rotation and small-scale swirl motions observed higher in the atmosphere.
Vortices in the solar photosphere  [PDF]
S. Shelyag,V. Fedun,R. Erdélyi,F. P. Keenan,M. Mathioudakis
Physics , 2012,
Abstract: Using numerical simulations of the magnetised solar photosphere and radiative diagnostics of the simulated photospheric models, we further analyse the physical nature of magnetic photospheric intergranular vortices. We confirm the magnetic nature of the vortices and find that most MHD Umov-Poynting flux is produced by horizontal vortex motions in the magnetised intergranular lanes. In addition, we consider possible ways to directly observe photospheric magnetic vortices using spectropolarimetry. Although horizontal plasma motions cannot be detected in the spectropolarimetric observations of solar disk centre, we find an observational signature of photospheric vortices in simulated observations of Stokes-V amplitude asymmetry close to the solar limb. Potential ways to find the vortices in the observations are discussed.
The Solar Photosphere: Evidence for Condensed Matter
Robitaille P. M.
Progress in Physics , 2006,
Abstract: The stellar equations of state treat the Sun much like an ideal gas, wherein the photosphere is viewed as a sparse gaseous plasma. The temperatures inferred in the solar interior give some credence to these models, especially since it is counterintuitive that an object with internal temperatures in excess of 1 MK could be existing in the liquid state. Nonetheless, extreme temperatures, by themselves, are insufficient evidence for the states of matter. The presence of magnetic fields and gravity also impact the expected phase. In the end, it is the physical expression of a state that is required in establishing the proper phase of an object. The photosphere does not lend itself easily to treatment as a gaseous plasma. The physical evidence can be more simply reconciled with a solar body and a photosphere in the condensed state. A discussion of each physical feature follows: (1) the thermal spectrum, (2) limb darkening, (3) solar collapse, (4) the solar density, (5) seismic activity, (6) mass displacement, (7) the chromosphere and critical opalescence, (8) shape, (9) surface activity, (10) photospheric/coronal flows, (11) photospheric imaging, (12) the solar dynamo, and (13) the presence of Sun spots. The explanation of these findings by the gaseous models often requires an improbable combination of events, such as found in the stellar opacity problem. In sharp contrast, each can be explained with simplicity by the condensed state. This work is an invitation to reconsider the phase of the Sun.
Convective shifts of iron lines in the spectrum of the solar photosphere  [PDF]
V. A. Sheminova,A. S. Gadun
Physics , 2010,
Abstract: The influence of the convective structure of the solar photosphere on the shifts of spectral lines of iron was studied. Line profiles in the visible and infrared spectrum were synthesized with the use of 2-D time-dependent hydrodynamic solar model atmospheres. The dependence of line shifts on excitation potential, wavelength, and line strength was analyzed, along with the depression contribution functions. The line shifts were found to depend on the location of the line formation region in convective cells and the difference between the line depression contributions from granules and intergranular lanes. In visible spectrum the weak and moderate lines are formed deep in the photosphere. Their effective line formation region is located in the central parts of granules, which make the major contribution to the absorption of spatially unresolved lines. The cores of strong lines are formed in upper photospheric layers where is formed reversed granulation due to convection reversal and physical conditions change drastically there. As a consequence the depression contributions in the strong line from intergranular lanes with downflows substantially increase. This accounts for smaller blue shifts of strong lines. In infrared spectrum the observed decrease in the blue line shifts is explained by the fact that their effective line formation regions lie higher in the photosphere and extend much further into the reversed granulation region due to the line opacity rise with the increase of line wavelength. Additionally the effective line formation depths of the synthesized visible and infrared Fe I lines and their dependence on line parameters is discussed.
Turbulence in the Solar Photosphere  [PDF]
K. Petrovay
Physics , 2000,
Abstract: The precise nature of photospheric flows, and of the transport effects they give rise to, has been the subject of intense debate in the last decade. Here we attempt to give a brief review of the subject emphasizing interdisciplinary (solar physics - turbulence theory) aspects, key open questions, and recent developments.
Stochastic coupling of solar photosphere and corona  [PDF]
Vadim M. Uritsky,Joseph M. Davila,Leon Ofman,Aaron J. Coyner
Physics , 2012, DOI: 10.1088/0004-637X/769/1/62
Abstract: The observed solar activity is believed to be driven by the dissipation of nonpotential magnetic energy injected into the corona by dynamic processes in the photosphere. The enormous range of scales involved in the interaction makes it difficult to track down the photospheric origin of each coronal dissipation event, especially in the presence of complex magnetic topologies. In this paper, we propose an ensemble-based approach for testing the photosphere - corona coupling in a quiet solar region as represented by intermittent activity in SOHO MDI and STEREO EUVI image sets. For properly adjusted detection thresholds corresponding to the same degree of intermittency in the photosphere and corona, the dynamics of the two solar regions is described by the same occurrence probability distributions of energy release events but significantly different geometric properties. We derive a set of scaling relations reconciling the two groups of results and enabling statistical description of coronal dynamics based on photospheric observations. Our analysis suggests that multiscale intermittent dissipation in the corona at spatial scales > 3 Mm is controlled by turbulent photospheric convection. Complex topology of the photospheric network makes this coupling essentially nonlocal and non-deterministic. Our results are in an agreement with the Parker's coupling scenario in which random photospheric shuffling generates marginally stable magnetic discontinuities at the coronal level, but they are also consistent with an impulsive wave heating involving multiscale Alfvenic wave packets and/or MHD turbulent cascade. A back reaction on the photosphere due to coronal magnetic reconfiguration can be a contributing factor.
Horizontal Magnetic Fields in the Solar Photosphere  [PDF]
V. A. Sheminova
Physics , 2009, DOI: 10.1134/S1063772909050126
Abstract: The results of 2D MHD simulations of solar magnetogranulation are used to analyze the horizontal magnetic fields and the response of the synthesized Stokes profiles of the FeI 1564.85 nm line to the magnetic fields. Selected 1.5-h series of the 2D MHD models reproduces a region of the network fields with their immediate surrounding on the solar surface with the unsigned magnetic flux density of 192 G. According to the magnetic field distribution obtained, the most probable absolute strength of the horizontal magnetic field at an optical depth of tau_5 = 1 (tau_5 denotes tau at lambda = 500 nm) is 50 G, while the mean value is 244 G. On average, the horizontal magnetic fields are stronger than the vertical fields to heights of about 400 km in the photosphere due to their higher density and the larger area they occupy. The maximum factor by which the horizontal fields are greater is 1.5. Strong horizontal magnetic flux tubes emerge at the surface as spots with field strengths of more than 500 G. These are smaller than granules in size, and have lifetimes of 3.6 min. They form in the photosphere due to the expulsion of magnetic fields by convective flows coming from deep subphotospheric layers. The data obtained qualitatively agree with observations with the Hinode space observatory.
Rossby rogons in atmosphere and in the solar photosphere  [PDF]
A. P. Misra,P. K. Shukla
Physics , 2012, DOI: 10.1209/0295-5075/100/55001
Abstract: The generation of Rossby rogue waves (Rossby rogons), as well as the excitation of bright and dark Rossby envelpe solitons are demonstrated on the basis of the modulational instability (MI) of a coherent Rossby wave packet. The evolution of an amplitude modulated Rossby wave packet is governed by one-dimensional (1D) nonlinear Schr\"odinger equation (NLSE). The latter is used to study the amplitude modulation of Rossby wave packets for fluids in Earth's atmosphere and in the solar photosphere. It is found that an ampitude modulated Rossby wave packet becomes stable (unstable) against quasi-stationary, long wavelength (in comparision with the Rossby wave length) perturbations, when the carrier Rossby wave number satisfies $k^2 < 1/2$ or $\sqrt{2}+13$ or $1/2
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