In addition, auras are referred to as "fx" in the database file. This is the same category as things like capes, wings, crab pack, etc. You can actually place them in any part slot in the db as the position of the effect is "baked in," as it were, allowing you to combine things like wings and trench coats, for example. One of my favorites is combining the crab pack fx with the Cosmic Corsair back piece, which is also an fx for some reason.
Another note: many fx like the crab pack will adopt the texture of whatever geometry is in that slot, which can create some neat or ugly effects. For the default texture, simply place the fx string for that object in its own slot.