Plasma is pulled by gravity. If you fly too close to a planet, the plasma will be pulled inside of it's field to have a disproportionate amount of plasma facing the gravity source. This could cause a variety of effects depending on how you envision your ship working such as causing your ship to be pushed toward or away from the planet, or causing your ship to go into an uncontrollable spin that rips it apart.

If you want ships to be able to get closer than the outer limits of the gravity well, consider that moving through an atmosphere at more than a few thousand kph can incinerate pretty much anything. Trying to fly through an atmosphere at warp speeds will experience the relativistic baseball affect as per the most commonly cited meem here on world builder: https://what-if.xkcd.com/1/

Plasma is pulled by gravitational tidal forces. These tidal forces on a ship at rest are negligible, but if the warp field is stretching the frame of the ship, then from the planet's frame, the ship is no longer a hundred meters long, but it is stretched across 100s of thousands of kilometers making these tidal forces of gravity more extreme the faster you go. So, if you fly too close to a planet, the plasma will be pulled inside of it's field to have a disproportionate amount of plasma facing the gravity source. This could cause a variety of effects depending on how you envision your ship working such as causing your ship to be pushed toward or away from the planet, or causing it to go into an uncontrollable spin that rips it apart.

If you want ships to be able to get closer than the outer limits of the gravity well, consider that moving through an atmosphere at more than a few thousand kph can incinerate pretty much anything. Trying to fly through an atmosphere at warp speeds will experience the relativistic baseball affect as per the most commonly cited meem here on world builder: https://what-if.xkcd.com/1/