edu.ucar.opensky::articles:24791 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-24T23:01:24.038502 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7wh2tgb Mercury's exospheric He I 58.4 nm emission: Dependence on the orbital phase 2021-10-14T00:00:00Z publication https://n2t.org/ark:/85065/d7wh2tgb https://doi.org/10.1051/0004-6361/202142155 Yoneda, M. author Dima, Gabriel author Berdyugina, S. V. author UCAR/NCAR - Library publisher Aims. Emission from helium atoms in Mercury's exosphere at 58.4 nm was observed by the Mariner 10 spacecraft in the 1970s. This emission is due to resonant scattering of solar radiation. Since Mercury's orbit is ellipsoidal, solar radiation and wind fluxes on Mercury vary along its orbit. Furthermore, the flux of the solar He I 58.4 nm emission observed on Mercury varies with Mercury's radial velocity with the Sun. Using model simulations, we demonstrate how Mercury's exospheric He I 58.4 nm emission varies due to the periodic changes in solar radiation and wind. Methods. The simulation is based on our Monte-Carlo model that accounts for changes in fluxes of the solar wind and radiation. Results. The model results indicate that the He I 58.4 nm brightness varies by between one and three orders of magnitude along the planet's orbit. These findings are strongly dependent on the intrinsic line width of the solar He I 58.4 nm emission. Conclusions. Although this variation has never been observed because Mariner 10 only sampled emission near Mercury's aphelion, we expect this variation to be observable by new missions, such as BepiColombo and Hisaki. Our results are also important for the characterization of exoplanets with ultraviolet space missions. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright author(s). This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. None eng geoscientificInformation