During September 1982 a group of U.S., West German, and Brazilian organizations evaluated the trigger mechanism of equatorial ionospheric bubbles in an ionospheric modification experiment in Brazil. The experiment involved the release of two barium chemical packages at an unstable point in the nighttime F layer. At this point, they would trigger a bubble of low ion density to rise into the middle and upper F regions. Following the release of the barium, an aircraft equipped with a UHF satellite receiver was flown in the shadow of the bubble. It mapped the growth of the resulting irregularities from their initial appearance until they grew to a width of 100 km or more. The experiment demonstrated that a bubble could be triggered by proper placement of the barium ions and that the resultant irregularities would have the appearance of naturally triggered equatorial ionospheric irregularities.