Occlude Lense Flare with Particle System

I have a scene set up with a directional light. This light has a flare on it which I've made to look like the sun. What I'm trying to do is create my own clouds for my scene using a particle system, instead of the clouds being part of the skybox. The problem I'm having is the flare from my directional light can be seen through the clouds. I've done some research on flares and it's my understanding that they are occluded by colliders. So if I were to create a massive plane above my scene with a collider on it, it would occlude the flare on my directional light. The problem is, I don't know how to achieve that with a particle system. I want the sun to disappear when it goes underneath a cloud and the collision section built into the particle system does not appear to give this effect.

Any ideas?