A subspace magneton pulse was a burst of polarized magnetic energy that was usually produced by a damaged warp core. (DS9: "Hippocratic Oath")
In 2372, the USS Rubicon detected a magneton pulse in the Bopak system that suggested a ship was in trouble. Upon their arrival at Bopak III, they discovered that it was actually created by a Jem'Hadar attack ship on the surface. The magneton pulse was later hidden after a dampening field was erected around the ship's warp engine. (DS9: "Hippocratic Oath")
Also that year, Doctor Lenara Kahn utilized a magneton pulse in her efforts to create an artificial wormhole. Conducting her experiments aboard the USS Defiant, Doctor Kahn's procedure involved using a target drone to send out the pulse, which would then react with a subspace tensor matrix to create an opening in the spacetime continuum. The magneton pulse created a feedback loop which destroyed the drone, but not before successfully creating a short-lived wormhole. (DS9: "Rejoined")
Near the year's end, a group of rogue Jem'Hadar used a magneton pulse to disperse their ship's ion trail after attacking Deep Space 9. (DS9: "To the Death")