  The question of how nonlinear interactions redistribute the energy of
fluctuations across available degrees of freedom is of fundamental importance
in the study of turbulence and transport in magnetized weakly collisional
plasmas, ranging from space settings to fusion devices. In this letter, we
present a theory for the dual cascade found in such plasmas, which predicts a
range of new behavior that distinguishes this cascade from that of neutral
fluid turbulence. These phenomena are explained in terms of the constrained
nature of spectral transfer in nonlinear gyrokinetics. Accompanying this theory
are the first observations of these phenomena, obtained via direct numerical
simulations using the gyrokinetic code {\tt AstroGK}. The basic mechanisms that
are found provide a framework for understanding the turbulent energy transfer
that couples scales both locally and non-locally.
