An electromagnetic pulse, or E.M. pulse, has the ability to disrupt or disable devices and technology which rely on electrical power, including radio and telecommunication signals. After the battle with Anubis in Antarctica, small random electromagnetic fields were detected by Prometheus during the cleanup effort, and it was eventually discovered that an F-302 gives off an E.M. pulse when it blows up. Carter had studied the phenomenon at Area 51 and had determined that it was most likely due to the concussive force of the explosion interfering with the artificial gravity field generated by the inertial dampeners.
Using this discovery, SG-1 later devised a plan to disable the Ori satellite weapon in orbit above Tegalus. By harvesting the inertial dampener from an F-302 and rigging it to a Caledonian missile, disguised by the F-302's radar jamming technology that made it invisible to Rand, SG-1 detonated an E.M. pulse over Rand, temporarily disabling communications with the satellite and making it vulnerable to an attack by an F-302. The plan worked, and Rand lost control of the satellite, however Daniel brokered a deal with the leaders of Rand, and the attack against the satellite was called off, giving Rand time to restore communications, which made the satellite a threat once more.
Cross Reference: Electromagnetic Pulse Generator, F-302, Ori Satellite Weapon
Episode Reference: Ethon