Dispel a self targeting spell emanating from within an antimagic field

So, a character has an artifact granting the ability to cast Holy Aura. Another character casts Antimagic Field and the two effects overlap, so that the origins of both spells are within both spell effects.

Can someone cast Dispel Magic on the Holy Aura effect since its radius (30ft) exceeds that of the Antimagic Field (10ft)?

The argument raised against being able to dispel it, is that since the effect is active on a creature, then it is the creature that must be targeted, differentiating this case from a Grease spell for example.