  Magnetohydrodynamic (MHD) turbulence is a cross-field process relevant to
many systems. A prerequisite for understanding these systems is to constrain
the role of MHD turbulence, and in particular the energy exchange between
kinetic and magnetic forms. The energetics of strongly magnetized and
compressible turbulence has so far resisted attempts to understand them.
Numerical simulations reveal that kinetic energy can be orders of magnitude
larger than fluctuating magnetic energy. We solve this lack-of-balance puzzle
by calculating the energetics of compressible and sub-Alfv\'enic turbulence
based on the dynamics of coherent cylindrical fluid parcels. Using the MHD
Lagrangian, we prove analytically that the bulk of the magnetic energy
transferred to kinetic is the energy stored in the coupling between the ordered
and fluctuating magnetic field. The analytical relations are in striking
agreement with numerical data, up to second order terms.
