  The role of the different helical components of the magnetic and velocity
fields in the inverse spectral transfer of magnetic helicity is investigated
through Fourier shell-to-shell transfer analysis. Both magnetic helicity and
energetic transfer analysis are performed on chosen data from direct numerical
simulations of homogeneous isothermal compressible magnetohydrodynamic
turbulence, subject to both a large-scale mechanical forcing and a small-scale
helical electromotive driving. The root mean square Mach number of the
hydrodynamic turbulent steady-state taken as initial condition varies from 0.1
to about 11. Three physical phenomena can be distinguished in the general
picture of the spectral transfer of magnetic helicity towards larger spatial
scales: local inverse transfer, non-local inverse transfer and local direct
transfer. A shell decomposition allows to associate these three phenomena with
clearly distinct velocity scales while the helical decomposition allows to
establish the role of the different helical components and the compressive part
of the velocity field on the different transfer processes. The locality and
relative strength of the different helical contributions are mainly determined
by the triad helical geometric factor.
