Time Series of Solar Granulation Images. III. Dynamics of Exploding Granules and Related Phenomena

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 minute duration. The results of this study show that the dynamics of exploding granules is strongly affected by their surroundings and that their appearance is closely related to the mesogranular flow field. 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 different types of strong downflows developing in the centers of granules. The motions of all these three phenomena—the expansion of exploding granules and the proper motions of the smaller dark structures, respectively—can reach velocities close to the sound speed in the solar photosphere. Another type of structure—narrow intergranular connections between granules—has also been studied. Our results show that these structures are real solar phenomena and are not caused by a variation of the image quality. Therefore, in following and describing their evolution, we try to find an explanation for their frequent occurrence.