There are many caterpillar species with that general form and pattern. Most likely a moth, and of those, a noctuid moth. You might need to let it fully grow, or find one pupating and containerize it to see the final result.

Many different moths would eat a variety of Composite family species (includes sunflowers), so no help there either.

Looks like a western yellow striped armyworm to me, but the picture isnt quite clear enough to tell. If there is one, there are hundreds closeby. The adults lay a mass of hundreds of eggs, two generations per year. And in my experience they are opportunistic feeders with few preferences, meaning they eat just about anything (at least in my veggie garden with flowers).

Beautiful caterpillar.