Space-Time Distribution of G-Band and Ca II H-Line Intensity Oscillations in Hinode/SOT-FG Observations

We study the space-time distributions of intensity fluctuations in 2 - 3 hour sequences of multi-spectral, high-resolution, high-cadence broad-band filtergram images (BFI) made by the SOT-FG system aboard the Hinode spacecraft. In the frequency range 5.5 < f < 8.0 mHz both G-band and Ca II H-line oscillations are suppressed in the presence of magnetic fields, but the suppression disappears for f > 10 mHz. By looking at G-band frequencies above 10 mHz we find that the oscillatory power, both at these frequencies and at lower frequencies too, lies in a mesh pattern with cell scale 2 - 3 Mm, clearly larger than normal granulation, and with correlation times on the order of hours. The mesh pattern lies in the dark lanes between stable cells found in time-integrated G-band intensity images. It also underlies part of the bright pattern in time-integrated H-line emission. This discovery may reflect dynamical constraints on the sizes of rising granular convection cells together with the turbulence created in strong intercellular downflows.Comment: 24 pages, 15 figure

Can cellular convection in a rotating spherical shell maintain both global and local magnetic fields?

A convection-driven MHD dynamo in a rotating spherical shell, with clearly defined structural elements in the flow and magnetic field, is simulated numerically. Such dynamos can be called deterministic, in contrast to those explicitly dependent on the assumed properties of turbulence. The cases most interesting from the standpoint of studying the nature of stellar magnetism demonstrate the following features. On a global scale, the convective flows can maintain a "general" magnetic field with a sign-alternating dipolar component. Local (in many cases, bipolar) magnetic structures are associated with convection cells. Disintegrating local structures change into background fields, which drift toward the poles. From time to time, reversals of the magnetic fields in the polar regions occur, as "new" background fields expel the "old" fields

О создании единого следственного органа в России

Time-averaged series of granulation images are analysed using COLIBRI, a purpose-adapted version of a code originally developed to detect straight or curvilinear features in aerospace images. The algorithm of image processing utilises a nonparametric statistical criterion that identifies a straight-line segment as a linear feature (lineament) if the photospheric brightness at a certain distance from this line is on both sides stochastically lower or higher than at the line itself. Curvilinear features can be detected as chains of lineaments, using a criterion modified in some way. Once the input parameters used by the algorithm are properly adjusted, the algorithm highlights ``ridges'' and ``trenches'' in the relief of the brightness field, drawing white and dark lanes. The most remarkable property of the trenching patterns is a nearly-universally-present parallelism of ridges and trenches. Since the material upflows are brighter than the downflows, the alternating parallel light and dark lanes should reflect the presence of roll convection in the subphotospheric layers. If the numerous images processed by us are representative, the patterns revealed suggest a widespread occurrence of roll convection in the outer solar convection zone. In particular, the roll systems could form the fine structure of larger-scale, supergranular and/or mesogranular convection flows. Granules appear to be overheated blobs of material that could develop in convection rolls due to some instabilities of roll motion.Comment: 16 pages, 7 figures; accepted by Solar Physic