(covers information from several alternate timelines)
Nucleonic particles accumulating on Enterprise's hull in a polaric field
A polaric field is a field of polaric radiation and nucleonic particles which can cause major explosions and temporal phenomena.
Enterprise NX-01 encountered a polaric field in the Delphic Expanse in 2153. The ship became trapped in the field when nucleonic particles flooded its plasma injectors, forcing a shutdown of its warp reactor. The particles then began to build up around the ship's hull, but it ultimately escaped by using the shuttlepods to tow the starship a small distance, producing enough momentum to pull Enterprise out of the field. (ENT: "Similitude")
In 2371, Captain Janeway used a tricorder to emit a polaric field to scan for "fractures in time". This timeline was later negated when the polaric ion explosion that created the aforementioned fractures was averted. (VOY: "Time and Again")