This is called convection current, but I think you have the mechanism backwards- hot air rises and cold air sinks. Cold air is more dense than hot air, essentially meaning it is “heavier.”

The “lighter” hot air rises and the “heavier” cold air sinks. Since it is cold high in the atmosphere, the hot air rising will eventually cool down, causing it to fall, replacing the air underneath it which will warm up and rise: thus creating convection current.