The high density, low temperature ionized cloud surrounding a pellet moving across a tokamak magnetic field forms a long field aligned 'ablation channel'. This plasma mass shields the pellet from the incident plasma electrons streaming toward the pellet along field lines. Therefore, the shielding capability of the cloud-the effective column ablation density intercepting the incident electrons-depends on the relative cross-field displacement between pellet and ablation channel. This transverse displacement is caused by the J⊥ × B Lorentz force, where the transverse current density passing through the channel J⊥ is powered by the motional E-field as seen in the reference frame co-moving with the pellet. It is shown that the currents inside the ablation channel are closed by background field aligned currents carried by outgoing shear Alfven waves. From ∇.J=0, one can obtain a self-consistent equation which describes the electrostatic field near the channel. The transverse force and deflection of the ablation channel are estimated from these results in order to determine the effective shielding length