  We theoretically study the coupling of electric charge and spin polarization
in an equilibrium and nonequilibrium electric transport across a two
dimensional Josephson configuration comprised of disordered surface channels of
a three dimensional topological insulator. In the equilibriun state of the
system we predict the Edelstein effect, which is much more pronounced than its
counterpart in conventional spin orbit coupled materials. Employing a
quasiclassical Keldysh technique, we demonstrate that the ground state of
system can be experimentally shifted into arbitrary macroscopic superconducting
phase differences other than the standard `$0$' or `$\pi$', constituting a
$\phi_0$-junction, solely by modulating a quasiparticle flow injection into the
junction. We propose a feasible experiment where the quasiparticles are
injected into the topological insulator surface by means of a normal electrode
and voltage gradient so that oppositely oriented stationary spin densities can
be developed along the interfaces and allow for directly making use of the
spin-momentum locking nature of Dirac fermions in the surface channels. The
$\phi_0$-state is proportional to the voltage difference applied between the
injector electrode and superconducting terminals that calibrates the injection
rate of particles and, therefore, the $\phi_0$ shift.
