相关论文: Sunspot simulations: penumbra formation and the fl…
There have been a few reports in the literature of counter-Evershed flows observed in well developed sunspot penumbrae, i.e. flows directed towards the umbra along penumbral filaments. Here we investigate the driving forces of such…
We investigate the instability of a tubular fluid membranes made of a water soluble surfactant. The tubules are obtained at high salinities. The instability is due to the introduction within the vesicle multilayer of an alkane. We measure…
The latitudinal distribution of starspots deviates from the solar pattern with increasing rotation rate. Numerical simulations of magnetic flux emergence and transport can help model the observed stellar activity patterns and the associated…
Numerical simulations have by now revealed that the fine scale structure of the penumbra in general and the Evershed effect in particular is due to overturning convection, mainly confined to gaps with strongly reduced magnetic field…
Structure formation in turbulence is effectively an instability of "plasma" formed by fluctuations serving as particles. These "particles" are quantumlike; namely, their wavelengths are non-negligible compared to the sizes of background…
aims: We study the recently discovered twisting motion of bright penumbral filaments with the aim of constraining their geometry and the associated magnetic field. methods: A large sunspot located $40\degr$ from disk center was observed at…
Three- and five-minute oscillations are commonly found in any sunspot. As they are modulated by the internal thermal and magnetic structures of a sunspot, therehence, they could be used as an effective tool for sunspot seismology. In this…
We consider the lifetimes of spots on the Sun and other stars from the standpoint of magnetic diffusion. While normal magnetic diffusivity predicts lifetimes of sunspots that are too large by at least two orders of magnitude, turbulent…
We present the computed phase diagram of columnar structures of soft spheres under pressure, of which the main feature is the appearance and disappearance of line slips, the shearing of adjacent spirals, as pressure is increased. A…
Coronal plumes are narrow, collimated structures that are primarily viewed above the solar poles and in coronal holes in the extreme ultraviolet, but also in sunspots. Open questions remain about plume formation, including the role of…
The generation of magnetic flux in the solar interior and its transport from the convection zone into the photosphere, the chromosphere, and the corona will be in the focus of solar physics research for the next decades. With 4m class…
We have employed a penumbral model, that includes the Evershed flow and convective motions inside penumbral filaments, to reproduce the azimuthal variation of the net circular polarization (NCP) in sunspot penumbrae at different…
A hypothesis for sunspot formation is the buoyant emergence of magnetic flux tubes created by the strong radial shear at the tachocline. In this scenario, the magnetic field has to exceed a threshold value before it becomes buoyant and…
We describe a scenario for the sunspot magnetic field topology that may account for recent observations of upflows and downflows in penumbrae. According to our conjecture, short narrow magnetic loops fill the penumbral volume. Flows along…
The hydrodynamic stability behaviour of a two-layer falling film is explored with a floating flexible plate on the top surface. The stress balance at the surface is modeled using a modified membrane equation. There is an insoluble…
The equilibrium structure of sunspots depends critically on its magnetic topology and is dominated by magnetic forces. Tension force is one component of the Lorentz force which balances the gradient of magnetic pressure in force-free…
In this work we selected one particular fibril from a high resolution solar chromosphere observation from the Dutch Open Telescope, and tried to obtain a broad picture of the intricate mechanism that might be incorporated in the multiple…
We interpret penumbral filaments as due to convection in field-free, radially aligned gaps just below the visible surface of the penumbra, intruding into a nearly potential field above. This solves the classical discrepancy between the…
It is believed that turbulence may have a significant impact on star formation and the dynamics and evolution of the molecular clouds in which this occurs. It is also known that non-ideal magnetohydrodynamic effects influence the nature of…
Penumbral filaments and light bridges are prominent structures inside sunspots and are important for understanding the nature of sunspot magnetic fields and magneto-convection underneath. We investigate an interesting event where several…