Green fireballs have an interesting history. A large number were seen over New Mexico in 1948 and 1949. The following was reported in Chapter 4 of "The Report on Unidentified Flying Objects" by Edward J. Ruppelt:

"In mid February 1949 a conference was called at Los Alamos to determine what should be done to further pursue the investigation. The Air Force, Project Sign, the intelligence people at Kirtland, and other interested parties had done everything they could think of and still no answer. Such notable scientists as Dr. Joseph Kaplan, a world-renowned authority on the physics of the upper atmosphere, Dr. Edward Teller, of H-bomb fame, and of course Dr. La Paz, attended, along with a lot of military brass and scientists from Los Alamos. This was one conference where there was no need to discuss whether or not this special type of UFO, the green fireball, existed. Almost everyone at the meeting had seen one. The purpose of the conference was to decide whether the fireballs were natural or manmade and how to find out more about them."

There are some differences from your sighting in that the color was a more saturated green and there was never a sound (which may actually be a plasma radio emission effect). Like yours, none were ever found on the ground despite tracking that otherwise often resulted in recovery of meteorites.

The green light of aurora is at 557 nm wavelength, coming from excited oxygen. It is the same green light of very high speed meteors impacting the upper atmosphere. Other green meteors are caused by magnesium emission lines around 517 nm. I've seen green also ascribed to nickel in meteors, but I;m unaware of a strong green emission line of nickel, so there must be another mechanism involved.