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Sonic boom doesn't explain what causes sound only how it piles up.

Similarily I don't see how it explains the glow. Photons get generated regardless of whether they pile up or not. It's a consequence of particles bumping into atoms not the whatever speed of light might be in this medium.

How is piling up important?

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Very shortly summarized, only if the particle is faster than the local speed of light, you get constructive interference between many atoms that were polarized by the moving particle.

For a slower than light particle, you also get emission, but it is completely random and thus does not give the well defined emission in a cone of Cherenkov radiation.

For a faster than light particle, the spherical suddenly line up to form a cone:

https://en.wikipedia.org/wiki/Cherenkov_radiation#/media/Fil...

Thank you. That's a very good explanation.

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