Just silver (PHB p148) your arrows.
No one knows whether or not nonmagical arrows fired by a magical bow are counted as being magical or not? That seems bizarre. We even have the first half of the first Adventure Path out (the second half was just released on WPN stores and goes to like 14-15th level). And still no one knows? This is important, one of my players are hesitating to playing an archer if he is dependent on the DM providing fresh amounts of magical arrows.
Just silver (PHB p148) your arrows.