J. Hirzberger et al., Time series of solar granulation images. III. Dynamics of exploding granules and related phenomena, ASTROPHYS J, 527(1), 1999, pp. 405-414
The evolution of exploding granules is studied by using a spatially as well
as temporally highly resolved time series of white-light images of 80 minu
te duration. The results of this study show that the dynamics of exploding
granules is strongly affected by their surroundings and that their appearan
ce is closely related to the mesogranular flow held. Comparing the behavior
of exploding granules with that of smaller dark structures-so-called dark
dots-and with the results of model simulations leads to the conclusion that
both phenomena, as well as a third newly found phenomenon (dark structures
occurring in the centers of granules that are approximately twice as large
as dark dots but smaller than typical centers of exploding granules) are d
ifferent types of strong downflows developing in the centers of granules. T
he motions of all these three phenomena-the expansion of exploding granules
and the proper motions of the smaller dark structures, respectively-can re
ach velocities close to the sound speed in the solar photosphere. Another t
ype of structure-narrow intergranular connections between granules-has also
been studied. Our results show that these structures are real solar phenom
ena and are not caused by a variation of the image quality. Therefore, in f
ollowing and describing their evolution, we try to find an explanation for
their frequent occurrence.