 The study investigates the thermodynamics of magnetically expanding plasma in a magnetic nozzle, Mn, and finds that the system can be divided into two regions with different thermodynamic properties due to the existence of isothermally behaving confined electrons. The study also suggests that ion acceleration should not be directly inferred from the value of polytropic exponent gamma underscore E because thermodynamic property of a Mn is influenced by both isothermally behaving confined electrons and adiabatically expanding electrons. This article was authored by Jun Young Kim, K.S. Chung, Siongkyol Kim, and others.