  We study intraenvironmental classical and quantum correlations in a thermal
machine, which is modeled as a driven quantum system coupled with thermal
reservoirs. We compute the mutual information, the quantum discord, and the
entanglement between two parts of the environment formed by oscillators
centered around two different frequencies. We show that there are only two
processes that generate time-extensive correlations in the long-time limit.
First, there is a resonant process which is responsible for the transport of
excitations between different environmental modes due to the absorption (or
emission) of energy from (or into) the driving field. Second, there is a
nonresonant process that transforms the energy from the external driving into
pairs of excitations in two environmental modes. We show that there is a regime
when the mutual information and the quantum discord between the parts of the
environment correlated by these two processes grow quadratically in time, while
entanglement production is time-extensive.
