Hi Tomer,

Are you referring to IsolatedGalaxy/galaxy0030/galaxy0030? This is an Enzo dataset, which has a number of runtime parameters encoded in the output file (actually in the galsxy0030 text file we use to signify the full dataset when loading it with yt). You can take a look at the Enzo documentation to see what each runtime parameter means:

I wasn't around when this dataset was generated, but my understanding is that it was generated purely for debugging purposes by Ji-Hoon Kim many years ago. The idea was to create an Enzo dataset that contains as many fields as possible as a test for yt's field detection machinery. This makes that some of the fields (e.g. the magnetic field variables for one) don't actually contain valid data. We tend to use it a lot in the documentation partly for historical purposes and also party because it's small and nice looking.

I don't think this dataset ever made it into a published paper, but it's setup is very similar to the ones described here:

Nathan