NOAA18 satellite TED and MEPED data across the auroral oval for the time interval from 1358UT to 1402 UT, September 12, 2024. 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. NOAA18 satellite was located at near Japan’s meridian, i.e. 50–64°N and 120–112°E at that time. We identified the location where the flux of 189 eV electron (black line) exceeds 10³ /cm²-s-sr-eV level as the equatorward boundary of the auroral oval. In this case, the timing is 1400 UT, and the geographic coordinate is 58.0°N, 116.3°E.