Make particles only visible in direct light?

I’m trying to create a particle emitter and material to simulate dust. One property of real dust that I want to reproduce is that dust is only visible in strong direct lighting, and practically invisible in other lighting conditions. But I can’t figure out how to do that with my particles.

Is there some way to get access to the lighting information in the material, so I could scale the alpha with the ambient light? Or a setting I can check that this material should not be lit by indirect lighting? Or can anyone tell me a better way to do what I want to do?

Did you ever find a way to achieve this effect? I’ve been struggling with it for a while. Seems like my particles are always visible, despite being set to ‘default lit’.