A reduced two-fluid model is constructed to investigate the geodesic acoustic mode (GAM).The ion dynamics is sufficiently considered by including an anisotropic pressure tensor and inhibited heat flux vector,whose evolutions are determined by equations derived from the 16-momentum model.Electrons are supposed to obey the Boltzmann distribution responding to the electrostatic oscillation with near ion acoustic velocity.In the large safety factor limit,the GAM frequency is identical with the kinetic one to the order of 1/q2 when zeroing the anisotropy.For general anisotropy,the reduced two-fluid model generates the frequency agreeing well with the kinetic result with arbitrary electron temperature.The present simplified fluid model will be of great use and interest for young researchers and students devoted to plasma physics.
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CAS Key Laboratory of Geospace Environment and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China;