Those are actually listed in the !hull_files.txt in that folder. Here's the full list.
sysburn - an effect used when a system has been disabled
hullburn - used when the ship has been "killed" and is burning
explode1 - ship explosion effect
explode2 - ship explosion effect with multiple particles
debris - ship parts that go flying when it explodes
fragburn - an effect for burning hull segments after explosion
So by default, sysburn is "sparkjet" and hullburn is "flamejet"
Oh duh! I looked in a couple, but I had already learned the relevant info from here, so I stopped bothering with those txt files. Thanks! I'll consult them in the future before bugging everyone