Heat is deposited to the Jovian ionosphere in the course of enforcement of corotation to the outer magnetosphere. The Joule heating rate is estimated for several possible causes of departure from the corotation by making use of a simple model of the magnetodisc. Following compression or expansion of the magnetosphere, the magnetospheric plasma superrotates or subrotates in consequence of conservation of the angular momentum, and thermal energy is deposited in the ionosphere at a rate of the order of 1012 W for about 105 s while rotational speed is adjusted toward the corotation with the planet. Outward diffisuion of the Iogenic plasma at a rate of 1029 amu/s also causes ionospheric heating at a rate of 1013 W as the ionosphere acts to drive the plasma toward the corotation. Day-night asymmetry in trajectory of rotational motion of plasma, owing to asymmetry in configuration of the magnetosphere, is also likely to produce energy dissipation of a similar magnitude as the rotational speed is adjusted continually. Thus the corotation enforcement current deposits as much heat as the dynamo current from Io and plays an important part in energetics and dynamics of the Jovian magnetosphere. The heating rate per unit area of the high-latitude ionosphere is more than ~10 erg/cm2 s, namely, orders of magnitude greater than the rate of the energy supply by the solar UV radiation. These numbers depend on the adopted height-integrated conductivity of 0.1 mho of the Jovian ionosphere.