  The ability of the neutron star surface to supply all or only part of the
charges filling the pulsar magnetosphere is crucial for the physics prevailing
within it, with direct consequences for the possible formation of pair creation
regions. We evaluate the conditions for $e^-$ emission from pulsar surfaces for
a simple Goldreich-Julian geometry taking both thermal and field emission
processes into account. Using recently published estimates for the equation of
state at the neutron star's surface, we show, that for a large range of $T_{\rm
surf}, B$ and $P$, the liberated charges will fully screen the accelerating
B-parallel electric field ${\rm E_\|}$. For surface temperatures $T_{\rm
surf}<2\cdot 10^5 $K a balance between field emission of electrons and
shielding of the field will occur. Even in the overidealised case of $T_{\rm
surf}=0$ one can expect a prodigious supply of electrons which will weaken the
accelerating ${\rm E_\|}$. We calculated the motion of electrons along selected
polar field lines numerically for the low temperature, field emission scenario
yielding their Lorentz factors as well as the produced radiation densities.
Inverse Compton and later curvature losses are seen to balance the acceleration
by the residual electric fields. We found that the conditions for magnetic pair
production are not met anywhere along the field lines up to a height of 1500
pulsar radii. We did not {\it a priori} assume an "inner gap", and our
calculations did not indicate the formation of one under realistic physical
conditions without the introduction of further assumptions.
