  We briefly compare in numerical simulations the relativistic ionization front
and electron bunch seeding of the self-modulation of a relativistic proton
bunch in plasma. When parameters are such that initial wakefields are equal
with the two seeding methods, the evolution of the maximum longitudinal
wakefields along the plasma are similar. We also propose a possible
seeding/injection scheme using a single plasma that we will study in upcoming
simulations works.
