Inner Boundary of the Heliosphere

There is no extensively accepted definition for the inner boundary of the heliosphere although the nomenclature——heliosphere——is increasingly used in the scientific presentations inthe space physics. After commenting some definitions of the inner boundary, the alfvenic points are suggested to be the inner boundary of the heliosphere. The definition is consistent with the concept of the wind sphere, and convenient for determination of the angular momentum loss of the Sun by the solar wind.