Long-term-averaged three-dimensional data-based models of the plasma sheet were used to study relationships between the density n, pressure P, and temperature T of the plasma and between the volume V and particle content N of a tube that contains 1 Wb of magnetic flux. Near midnight a typical unit flux tube located at x0 = -11.5 RE was found to contain only 30% as many particles as a typical unit flux tube located at x0 = -29.5 RE. The average value of the adiabatic compression parameter PV5/3 was only 20% and 15% as large at x0 = -11.5 RE for ions and electrons, respectively, as at x0 = -29.5 RE. A decrease of the average N and PV5/3 can be caused by the ejection of plasmoids during reconnection. Such ejections are likely to be important beyond 20 RE. Fast flows, flux tube interchange, drift effects, and a heat flux are likely to be more important at lower altitudes. The entropy parameter Pn-5/3 was found to be relatively uniform throughout the region studied. The energy parameter TV2/3 decreased by 40% for ions and 10% for electrons near midnight between -29.5 and -11.5 RE. These energy parameter changes suggest that the most energetic ions and electrons are either being deenergized or preferentially lost, processes that may be associated with gradient and curvature drifts through the sides of the convecting flux tubes or by wave instabilities and a parallel heat flux.