Ribbons coming off of the back of the INDYCARS @ Iowa?

When i was watching the indy car race a couple weekends ago it looked like there were Ribbons coming off the back of the wins in the corners especially. Was this air? I know nothing is tied to the rear spoiler and you could only see it entering, and during the corners clearly. I mean.. explain to me what it was? if it was air, why could we see it?