Aura of Prescience, free action to activate?

[Axoren]

From the Void School of Wizardry, is Aura of Prescience a free action to activate each round?

Quote:

Aura of Prescience (Su)

At 8th level, you can emit a 30-foot aura of void energy for a number of rounds per day equal to your wizard level. Allies within this aura gain a +2 insight bonus on ability checks, attack rolls, damage rolls, saving throws, and skill checks. These rounds do not need to be consecutive.

It seems like its activation is like that of non-consecutive rounds of Fly, where it simply just happens. You decide that the round is one of those rounds, like activating Power Attack, rather than spending an action to make it happen.

But there's no clear interpretation since generally Supernatural Abilities without a listing are either constantly in effect (which this obviously isn't) or a standard action to activate.

For a wizard, spending a standard action each round to produce this aura is very not worth the action economy warranting Level 8 access. So it's my belief that it's intended as a Free Action to activate. However, my group is of the other school of thought.

[Mark Seifter]

Supernatural abilities are a standard action to activate by default, but leaving the ability "on" once activated generally wouldn't take additional actions.

[Axoren]

Mark Seifter wrote:

Supernatural abilities are a standard action to activate by default, but leaving the ability "on" once activated generally wouldn't take additional actions.

If this is the intention, then what sort of action would it be to cease the aura? Or to suppress the effects for a single round without terminating it (so that it does not take a standard on the next round to bring back up)?