Subauroral ground‐based observations have found several cases of isolated proton auroral emissions equatorward of the proton auroral oval when Pc1/EMIC waves in the frequency range of the He+ ‐band ion cyclotron wave appear on conjugate ground magnetometers. Quantitative estimates of the spatial distribution of the EMIC waves should be invaluable information for quantitative estimates of the loss rates of radiation‐belt particles. This chapter presents a study in which isolated proton aurora (IPA) occurrence, location, and size were statistically investigated for the first time to examine the wave‐particle interaction region in the inner magnetosphere. It first describes the observation site and instrumentation for the study, and then describes the event detection method. Later, statistical results are reported. The equatorial projections of IPA source locations and two‐dimensional (2D) structures are estimated by magnetic field tracing.