A warp bubble, also known as a static warp bubble or static warp field, is a type of subspace deformation, a warp in the fabric of space. Some individuals, such as those native to the planet Tau Alpha C, were capable of manipulating warp bubbles with their minds.
A person could become trapped within a warp bubble; escape would depend on creating a stable threshold between the warp bubble and the outside environment. Prior to 2367, there were no known practical examples of an escape but the theoretical database suggested the threshold would manifest itself as a dynamic atmospheric disturbance of great intensity.
In 2367, Ensign Wesley Crusher performed an experiment aboard the USS Enterprise-D based on Kosinski's warp equations, wherein he created a warp bubble within the warp drive of the Enterprise. The bubble remained roughly stable at a field distortion level of 1,283 × 3,695 millicochranes. During the experiment, Wesley's mother, Doctor Beverly Crusher, became trapped inside the warp bubble. She was essentially caught in her own parallel universe, where her thoughts at the very moment she was trapped shaped her reality. As Dr. Crusher's thoughts were of losing old friends, a universe was created where the crew of the Enterprise disappeared one by one, eventually leaving her alone on the vessel. The bubble began to collapse, causing the remainder of the universe and eventually the Enterprise itself to gradually vanish as well.
As Wesley and the Enterprise crew attempted to retrieve Dr. Crusher before the bubble collapsed, they were visited by the Traveler, a Tau Alpha C inhabitant, who assisted Wesley in keeping the bubble stable long enough to create a threshold between both realities, which took the form of a violent vortex. As Dr. Crusher began to realize what was happening, she located the threshold and jumped through it just before the bubble completely collapsed, returning to her own reality. (TNG: "Remember Me")
Trionic initiators in warp coils were known to unintentionally produce warp bubbles and other subspace deformations when they were adjusted. Such initiators were used on the USS Hera. (TNG: "Interface")