The beam detonates once it hits the poor widdle force of nature, the impact of all that magic strong enough to lift him off the ground as if it were hit with an Ursa-sized Shoryuken. The impact also forces it to let go of you, and your foot-jets were already engaged in advance for this moment, allowing you to continue floating in the air right where you were as he hits the ground with a fittingly loud and apocalyptic CRASH, the oversized critter out like a light.