We have studied the spatial distribution of the long-lived granules from a population of 346 granules located in a photospheric region 37"x37". Our study 13 based on an exceptional sequence of photos taken by R. Muller at the Pic-du-Midi Observatory on May 16, 1979. We have determined the lifetime of all the granules situated in this rectangular photospheric region. For the determination of the mean lifetime (15.5 min) we have used a method recently developed (Alissandrakis et aI.. 1987), that permits to define accurately the mean lifetime. Finally we have studied the spatial distribution of the long-lived granules. As long-lived granules we consider all the granules with lifetime greater than the mean lifetime of the population. We found that the long-lived granules are not randomly distributed in the area under study, but they are located in well defined regions with mean length 0"-10" and mean width 2"-4". This result seems to confirm our suggestion (Dialetis et al. 1986) that there are at least two families of granules as for as their lifetime is concerned. We discuss the possible causes of the existence of regions characterized by slower evolutionary process.
We have studied the height dependent characteristics of the Evershed flow in the photosphere, chromosphere and chromosphere-corona transition region. We have used the Multichannel Subtractive Double Pass Spectrograph (MSDP) to
obtain line of sight velocity maps in Hα, the Meudon magnetograph for mapping the photospheric velocity field and the Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission (SMM) spacecraft to obtain line of sight velocities in C IV, in sunspot regions. Our emphasis was on the large scale,
quasi-stationary characteristics of the flow. In the photosphere the velocity is low above the umbra and shows a maximum above the penumbra. In addition to the reversal of the flow in the chromosphere both the characteristic scale of the flow and the velocity are larger; the velocity maximum is located outside the photospheric penumbra. In the chromosphere-corona transition
region there is a clear tendency for a chromospheric-type Evershed effect with a predominantly horizontal flow. The velocity is greater than in the chromosphere, but the characteristic scale of the flow is about the same. In addition to the Evershed flow, C IV observations show upflows above the umbra with a velocity of about 15 km/sec.