  We derive and test a new heuristic theory for third-order structure functions
that resolve the forcing scale in the scenario of simultaneous spectral energy
transfer to both small and large scales, which can occur naturally in rotating
stratified turbulence or magnetohydrodynamical~(MHD) turbulence, for example.
The theory has three parameters, namely the upscale/downscale energy transfer
rates and the forcing scale, and it includes the classic inertial range
theories as local limits. When applied to measured data, our global-in-scale
theory can deduce the energy transfer rates using the full range of data,
therefore it has broader applications compared with the local theories,
especially in the situations where the data is imperfect. In addition, because
of the resolution of forcing scales, the new theory can detect the scales of
energy input, which was impossible before. We test our new theory with a
two-dimensional simulation of MHD turbulence.
