  The nonlinear thermal balance equation for classical plasma in a toroidal
geometry is analytically and numerically investigated including ICRH power. The
determination of the equilibrium temperature and the analysis of the stability
of the solution are performed by solving the energy balance equation that
includes the transport relations obtained by the classical kinetic theory. An
estimation of the confinement time is also provided. We show that the ICRH
heating in the IGNITOR experiment, among other applications, is expected to be
used to trigger the thermonuclear instability. Here a scenario is considered
where IGNITOR is led to operate in a slightly sub-critical regime by adding a
small fraction of ${}^3He$ to the nominal $50$$\%$-$50$$\%$ Deuterium-Tritium
mixture. The difference between power lost and alpha heating is compensated by
additional ICRH heating, which should be able to increase the global plasma
temperature via collisions between ${}^3He$ minority and the background $D-T$
ions.
