Solar EUV flux from the triple ionosophere PhotoMeter onboard the Fengyun-3E satellite

The Triple Ionosphere Photometer (TRIPM) is a scientific payload aboard the Fengyun-3E (FY-3E) satellite, which operates in a dawn−dusk orbit. It is primarily designed for nadir observations of airglow emissions at OI 135.6 nm and N₂ Lyman-Birge-Hopfield (LBH) bands. Due to the satellite’s dawn−dusk orbital characteristics, most of TRIPM’s field of view remains in a semi-illuminated condition. Therefore, compared with airglow data of the same bands acquired under purely daytime or nighttime conditions, applying TRIPM data poses greater challenges. This study presents the first attempt to use TRIPM data for retrieving solar extreme ultraviolet (EUV) flux. Our results demonstrate that by utilizing TRIPM data in regions where photoelectron excitation dominates as the primary radiation source, the solar EUV flux (denoted as Q_EUV) can be retrieved. Comparisons with data from the SOHO/SEM instrument reveal excellent consistency, with a seasonal correlation coefficient (R) of at least 0.95. This work thus offers a new avenue for solar EUV flux acquisition and expands the application range of TRIPM data.