Fundamental Relation for the Ideal Gas in the Gravitational Field and Heat Flow

We formulate the first law of global thermodynamics for stationary states of the ideal gas in the gravitational field subjected to heat flow. We map the non-uniform system (described by profiles of the density and temperature) onto the uniform one and show that the total internal energy [Formula: see text] is the function of the following parameters of state: the non-equilibrium entropy [Formula: see text] , volume V, number of particles, N, height of the column L along the gravitational force, and renormalized mass of a particle [Formula: see text]. Each parameter corresponds to a different way of energy exchange with the environment. The parameter [Formula: see text] changes internal energy due to the shift of the centre of mass induced by the heat flux. We give analytical expressions for the non-equilibrium entropy [Formula: see text] and effective mass [Formula: see text]. When the heat flow goes to zero, [Formula: see text] approaches equilibrium entropy. Additionally, when the gravitational field vanishes, our fundamental relation reduces to the fundamental relation at equilibrium.