Interference between the Atmospheric and Solar Oscillation Amplitudes

We propose to detect the interference effect between the atmospheric-scale and solar-scale waves of neutrino oscillation, one of the key consequences of the three-generation structure of leptons. In vacuum, we show that there is a natural and general way of decomposing the oscillation amplitude into these two oscillation modes. The nature of the interference is cleanest in the $\bar{\nu}_e$ disappearance channel since it is free from the CP-phase $\delta$. We find that the upcoming JUNO experiment offers an ideal setting to observe this interference with more than $4\,\sigma$ significance, even under conservative assumptions about the systematic uncertainties.