At some stage market was bound to correct. It had spent more than 600 days above 200MA.
How far correction will go we do not know. But typical corrections are 8 to 10% and this correction is yet to reach that level, barring small caps which have corrected more than that.
Down moves are characterised by frequent counter trend bounce so one is again due in next couple of days.
Mot corrections since 2009 bottom have been few weeks affair, we will see if this one is different.
All corrections since 2009 has ended with some sort of Fed intervention . Sometime intervention has been just verbal intention. So watch for signs of that.