>>DonHop+(OP)
Well, it's possible that it's too chaotic. As Lem points out in the story, we don't know enough about plasma physics to know what kinds of patterns can develop, persist, and reproduce over time in such an environment: true in 01964 and, I think, still true despite substantial advances since then. Maybe, as the story suggests, there's a sufficiently rich set of them that the Sun is teeming with life, with civilizations rising and falling every few hours. But maybe in such hot temperatures only very large structures are stable, like the convection cells we see, so that for purposes of life the whole sun is the size of a ribosome, operating on a time scale a billion times slower.