2-D multiline spectroscopy of the solar photosphere

The structure and dynamics of the photosphere are investigated, with time series of broadband and monochromatic images of quiet granulation, at the solar disk center. Images were acquired with the IPM observing mode at the THEMIS telescope. Velocity and line center intensity fields, derived from the observation of three different photospheric lines, are used to study velocity and intensity patterns at different heights in the photosphere. Automatic segmentation procedures are applied to velocity and intensity frames to extract solar features, and to investigate the dependence of their properties at different scales and heights. We find a dependence of the statistical properties of upflow and downflow regions on the atmospheric height. Larger granules, passing through a great part of the photosphere, are used to investigate the damping of convective motions in stably stratified layers. The results suggest the occurrence of an intense braking in the deep photosphere (first ~120 km). Furthermore, we investigate the temporal and spatial evolution of velocity fields, deriving typical time scales of dynamical processes relative to different solar features. In particular, for two selected isolated exploders, we reveal a velocity deceleration in the central region since the early phase of their fragmentation.

[1]  Luigi de Luca,et al.  Image restoration in thermo-fluid-dynamic applications of IR digital imagery , 1990, Other Conferences.

[2]  B. R. Hunt.  2 – Image Restoration , 1984 .

[3]  U. Jørgensen,et al.  Models of late-type stellar photospheres , 1994 .

[4]  S. Sofia,et al.  Modeling Convection in the Outer Layers of the Sun: A Comparison with Predictions of the Mixing-Length Approximation , 1996 .

[5]  Investigation of temperature and velocity fluctuations through the solar photosphere with the Na I D lines , 2001 .

[6]  F. Cavallini.  The Italian Panoramic Monochromator , 1998 .

[7]  M. Rast.  On the nature of exploding granules and granule fragmentation , 1995 .

[8]  Robert F. Stein,et al.  Simulations of Solar Granulation. I. General Properties , 1998 .

[9]  M. Koschinsky,et al.  High resolution 2D-spectroscopy of granular dynamics , 2001 .

[10]  R. Canfield.  The height variation of granular and oscillatory velocities , 1976 .

[11]  Arnold Hanslmeier,et al.  Time Series of Solar Granulation Images. I. Differences between Small and Large Granules in Quiet Regions , 1997 .

[12]  Graham Williams,et al.  Non-symmetrical dielectric relaxation behaviour arising from a simple empirical decay function , 1970 .

[13]  M. Rast.  The Thermal Starting Plume as an Acoustic Source , 1999 .

[14]  A. M. Title,et al.  Statistical Properties of Solar Granulation Derived from the Soup Instrument on Spacelab 2 , 1988 .

[15]  P. Mein,et al.  Temporal height properties of the exploding granules , 2001 .

[16]  T. Rimmele,et al.  Dark lanes in granulation and the excitation of solar oscillations , 1995 .

[17]  M. Dahlem,et al.  Star formation activity in spiral galaxy disks and the properties of radio halos: Observational evidence for a direct dependence , 1995 .

[18]  Owen Gingerich,et al.  The Harvard-Smithsonian reference atmosphere , 1971 .

[19]  Random walks on fractals and stretched exponential relaxation. , 2000, Physical review. E, Statistical, nonlinear, and soft matter physics.

[20]  H. Holweger,et al.  The photospheric barium spectrum: Solar abundance and collision broadening of Baii lines by hydrogen , 1974 .