When Sokar fired a particle beam accelerator through the wormhole, the space between the event horizon and the iris was enough to allow high energy subatomic particles to reintegrate and decay as they were bombarded against the iris, moving at near-light velocities. Modulating the particle stream created an image and a means of communication as well as intense heat, up to 200°F in the gateroom, and 6 to 8 times that for the iris itself.
When the stargate on Edora was buried by a meteor strike, molten naquadah from the impact hardened above the active event horizon like an iris, allowing the gate to be reactivated, but not permitting matter to reintegrate on the other side. Carter used the technology learned from Sokar to build a particle beam accelerator to be directed through the stargate at the buried Edoran gate. The subatomic particles bombarding the naquadah produced enough energy and heat to melt the hardened barrier over the gate, and the unstable vortex of gate activation created a small cavern large enough for matter to reintegrate and to allow one person to reach the other side. Teal'c volunteered for the mission which uncovered the stargate and restored contact with the planet.
Cross Reference: Edora, Sokar
Episode Reference: Serpent's Song, A Hundred Days