NOAA18 satellite TED and MEPED data across the auroral oval for the time interval from 1430 UT to 1435 UT, March 26, 2025. The energies of TED electron differential fluxes are 189, 844, 2,595, and 7,980 eV as colored by black, blue, green, and red, respectively. The energies of MEPED proton differential fluxes are 39, 115, 332, 1105, and 2723 keV as colored by black, blue, green, red and yellow, respectively. The NOAA18 satellite was located at near Japan’s meridian, i.e. 52–69°N and 112–98°E at that time. The location where the flux of 189 eV electron (black line) exceeds 10³/cm²-s-sr-eV level is identified as the equatorward boundary of the auroral oval. In this case, the timing is 1431 UT, and the geographic coordinate is 58.6°N, 109.0°E.