Lin, Bodenheimer, Richardson, 1995

Schematic of the migration of a giant planet inward. A giant planet of greater than 0.1 Jupiter masses gravitationally clears a gap. The viscous disk drains inward, carrying the young giant planet with it. When the planet reaches the magnetically-cleared hole within 0.1 AU of the star in the center, the viscous draining ceases. The planet may remain parked at the outer edge of that hole.