Speaking of the Instantaneous duration, I think people are maybe stretching its definition a bit too far. For starters, how long is instant? 1 second? 1 millisecond? It seems pretty clear to me that this duration was put in the game simply to show a relatively short period of time that happens in the space of the character's action. A melee attack or ranged attack is considered "instant" in this game, even though in real life swinging a sword or shooting a bow takes time. Fireball is also instant, yet Evocations like this only create their energy for the duration, and then it disappears. Fireball lasts only long enough to travel to its target area and explode. Once that happens, no fire remains behind. But what about instantaneous conjuration (creations) that are used as attack spells, like orbs and melf's acid arrows? Wouldn't their effect persist even after the magic that created them has gone?
Setting aside the absurdity that a globe of energy is an "object," I'm pretty sure that they would not persist. A globe of fire, even if it remains after the "instant" of its conjuration, would immediately dissipate in the air. A globe of acid will soon dissolve after coming in contact with other chemicals. A globe of sound will "detonate" and be gone. A globe of electricity will pass through whatever matter can conduct it before grounding out. If these "objects" were merely an instantaneous creation, which the caster then throws, there still has to be magic involved to explain how they survive the travel time to their target rather than just immediately exploding or evaporating in the caster's hand. And that's why I think an antimagic field blocks these spells.
But what about an orb of force? Force is, by its very nature, pure magical energy, impervious, indestructable, and something that exists through magic alone, never in nature. What happens to it? Does it also dissolve instantly, since force requires magic to sustain it? Or does it remain in the world forever as an instaneous and truly real and permanent creation? I think only the former makes sense. Force, by its very nature, pure magical energy given shape. Unlike fire, electricity or sound, nothing exists in nature that can sustain this energy, so it too, would disipate immediately after being conjured. Only a source of magic can sustain it long enough to reach its target and deal damage. And an antimagic fields block all magic.
