GRANULATION AND MAGNETISM IN THE SOLAR ATMOSPHERE

The properties of the photosphere in magnetic and non magnetic regions , at two levels in the solar atmosphere, have been studied, using two virtually simultaneous time sequences of 109 mn duration of CCD images taken at the Vacuum Tower Telescope of the Sacramento Peak Observator y. The selected wavelengths correspond to the true continuum and to th e wing of the MgIb(1) line, where brightenings are taken as proxies of magnetic elements. Averaged intensities, intensity fluctuations and h orizontal motions in different regions and levels of the photosphere h ave been compared. We obtained various results concerning: the intensi ties inside and outside an active region showing different behaviours: the granulation keeping a kind of remnant structure at the continuum level; the mapping of proper motions of the granules imaged in the con tinuum outlining clearly the super-granular cells in the deepest layer s of the photosphere; the ''freezing'' influence of the magnetic field on these motions in active regions; and the temporal variation of the correlation between images at the two heights indicating that intensi ty variations at the higher level precede those of the lower one. Thes e results are briefly discussed and compared with previous ones and wi th published model calculations.