A Delta Quadrant world whose civilisation is wiped out by a polaric ion explosion, to which Janeway and Paris are thrown back one day before the disaster in Time and Again.
This unnamed planet is the setting of Time and Again. Voyager is struck by a shock wave and traces it to a world where every living thing has just been killed by a detonation of polaric ion energy, a notoriously unstable power source.
Subspace fractures left by the blast pull Janeway and Paris a day into the past. They find a thriving society of roughly industrial level, arguing over polaric power, and fall in with a group of protesters led by Pe'Nar Makull who plan to break into a power station. A local boy, Latika, attaches himself to them.
Janeway works out that the explosion is set off not by the protesters but by her own crew's attempt to rescue her from the future. She seals the fracture, and the disaster never happens.