Define "down" please. Error code? Infinite loading? What are we looking at?
The problem seems to be that the authentication servers are down, but the game servers are still up. Meaning, if you are in the game, game still working. If you were logged in and haven't force closed, you might still be able to get back in if your authentication token hasn't expired yet. But if you are trying to log into the game or your game client has to log you back in (you force closed, say), then that process is currently busted.