Summary of a sporadic E event on July 4, 2019. (a) Time-series data of the critical frequency of Es layer (foEs) obtained at four ionosondes in Japan. The vertical axis represents the location of ionosondes (Wakkanai, Kokubunji, Yamagawa, and Okinawa) and the color represents the critical frequency in MHz. (b) Anomalous propagation data in NAV channels in a format of spectrogram obtained at the Rx station in Oarai, Japan.