grounded character attacking hovering character, they are in base contact, hovering character has Energy Shield, is grounded character rolling VS unmodified defense or defense +2

thanks in advance for the answer

You only get the ES/D if you are the target of a ranged attack, so it all depends on what type of attack the non-flyer (the correct term here) is making.

If for example the non-flyer is V Havok then he can just make a close combat attack for 4 damage and bypass ES/D. If it were someone with RCE though, and you wanted the RCE bonus, you would have to make a ranged attack and the hovering flyer would get the ES/D bonus to their defense.

thanks!