How do wingtip vortices behave in ground effect with no wind?

Wingtip vortices are a product of lift generation, where the high-pressure air under the wing spills over to the low-pressure area on top, creating rotating columns of air. In ground effect, which occurs when an aircraft is close to the runway surface, these vortices behave differently than they do at higher altitudes.

When an aircraft is in ground effect, the vortices tend to stay closer to the ground and do not dissipate as rapidly as they would if the aircraft were further away from the surface. As the aircraft moves down the runway, the wingtip vortices begin to move outward and can spread apart as the forward motion induces a relative wind that helps separate them. This spreading is especially observed at lower airspeeds around 5 knots, which is a transition speed during takeoff and landing.

Therefore, the correct answer indicates that as the aircraft moves, the wingtip vortices do indeed move apart under ground effect conditions, reinforcing their presence on the runway and demonstrating the unique behaviors of vortices in such close proximity to the ground.