How to control AirPort wireless radio from the command line?
See OSX Daily - Enable and Disable AirPort Wireless from the Command Line in Mac OS X.  Quote:


  Turn Airport Off via Command Line
  networksetup -setairportpower airport off
  
  Turn Airport On via Command Line
  networksetup -setairportpower airport on
  
  You won’t see any confirmation in the Terminal that the command
  succeeded or failed, but if you watch the AirPort menu icon you will
  see the bars disappear indicating the wireless interface is turned
  off, or reappear indicating that wireless is activated again.


NOTE: In OS X Lion, use the hardware name above instead of airport,
e.g. networksetup -setairportpower en1 off.