Recently I discovered that using the Circle of Protection spell in conjunction with the Atronach perk or any other spell absorption will allow your magicka to fill rapidly as long as you stay within the circle.
Any thoughts on this?

The Atronach Perk in Alteration will absorb enough of some Conjurations to the point where the spells do not work. My higher level Alterationists can actually can stand in a Dragons attack to recover from casting Dragonhide.

I discovered it too and was so excited that even made a http://www.youtube.com/watch?v=2JQ0DGglu9I&feature=plcp&context=C4964a3bVDvjVQa1PpcFMqxcyHKXsgFj_cqNCeLz4ud-J-NY3pUmc%3D describing how to get this ability.
Because Circle of Protection is not being absorbed by default.
As for me.