How do I change how much gravity is affecting my player mid game

Ok so I want to use the standard character controller that unity is giving me in my game.
The game is based on base jumping so I want to be able to press a button (deploy my chute) and change the amount of gravity affecting me in the middle of the game (while I am falling).
The problem is I have no idea where to start. The script that unity gives you is very long and scary and I know that if I try to edit it I’m going to screw up.
I’d appreciate any help.
Thanks

Physics.gravity = new Vector3(0, -1.0F, 0);

http://docs.unity3d.com/ScriptReference/Physics-gravity.html