Aft nacelle associative

The aft nacelle associative was a field pattern associated with warp modulation; it was of the highest energy level of the series.

When Geordi La Forge was traveling in the Type 15 shuttlepod Onizuka to Risa and wanted to pass the time, he played a trivia game with the computer. Listing all field patterns associated with warp modulation in order of decreasing energy was one of the questions. (TNG: "The Mind's Eye")

According to a trimmed line from the episode's script, forward saucer associative would have been the next highest level.