Study of FY-3D Ionospheric Photometer (IPM) Response to the Extreme Magnetic Storm on May 11, 2024

With the launch of the FY-3D satellite on November 15, 2017, the Far Ultraviolet Ionospheric Photometer (IPM) on board enables measurements of nighttime 135.6nm airglow emissions generated by the recombination of O⁺ ions and electrons, as well as daytime emissions from OI 135.6nm and N₂LBH due to photoelectron impact on atomic oxygen and molecular nitrogen. These measurements can obtain the key parameters such as nighttime peak electron density N_mF₂ and daytime O/N₂. The paper analyzes the response of IPM data during the extreme magnetic storm event on May 11, 2024. The study results of daytime data indicate that during the event, the O/N₂ decreased at all latitudes compared to geomagnetically quiet days. This finding can be used to explain the negative storm effects observed in IGS TEC. the study of nighttime data reveals that during magnetic storms, the intensity of 135.6nm increases significantly across all latitudes compared to geomagnetically quiet days, with an increase by up to three orders of magnitude. The enhancement persists from the storm main phase through the recovery phase. However, corresponding TEC data does not show such a pronounced increase. Furthermore, the stray light channel measuring radiation contribution above 190nm wavelength also exhibits a significant increase during magnetic storm days. This further indicates that the enhancement of nighttime 135.6nm radiation is not solely derived from ionospheric contributions.