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

With the launch of the FY-3D satellite on 15 November 2017, the far ultraviolet Ionospheric Photometer (IPM) on board enables measurements of nighttime 135.6 nm airglow emissions generated by the recombination of O⁺ ions and electrons, as well as daytime emissions from OI 135.6 nm and N₂ LBH due to photoelectron impact on atomic oxygen and molecular nitrogen. These measurements can obtain the key parameters such as nighttime peak electron density <italic>N</italic>_m<italic>F</italic>₂ and daytime O/N₂. The paper analyzes the response of IPM data during the extreme magnetic storm event on 11 May 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 135.6 nm 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 190 nm wavelength also exhibits a significant increase during magnetic storm days. This further indicates that the enhancement of nighttime 135.6 nm radiation is not solely derived from ionospheric contributions.