Effects of Inner Alfv\'{e}n Surface Location on Black Hole Magnetospheres in the Force-Free Limit

An energy extracting black hole magnetosphere can be defined by the location of its inner Alfv\'{e}n surface, which determines the rate of energy extraction along a given magnetic field line that passes through it. Despite its defining role, it is still largely uncertain how the location and nature of the inner Alfv\'{e}n surface might correspond to changes in magnetosphere structure. In this talk I will present simple force-free black hole magnetospheres obtained numerically that encompass a wide range of Alfv\'{e}n surface locations. In particular the differences between magnetospheres with an Alfv\'{e}n surface near the horizon and an Alfv\'{e}n surface near the boundary of the ergoregion will be discussed, along with what those differences might imply about energy extracting black hole magnetospheres in general.