SMILE SXI can be used to track solar wind composition

ABSTRACT Continuous monitoring of solar wind ion composition is essential for understanding solar-terrestrial interactions, particularly the solar wind charge exchange (SWCX) signal. The SWCX signal can be observed via soft X-ray emissions ($<$2 keV) that result from interactions between highly ionized solar wind particles (e.g. $\mathrm{O^{7+}}$, $\mathrm{O^{8+}}$, $\mathrm{C^{6+}}$) and neutral atoms, occurring throughout the heliosphere and planetary environments, including Earth’s exosphere. This paper investigates the potential of the upcoming Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission, with its Soft X-ray Imager (SXI), to remotely monitor solar wind composition changes via spectral analysis of the SWCX emission. We simulate SXI spectra based on three XMM–Newton observations of SWCX emission that occurred under different solar wind input conditions. The variations between the simulated SXI spectra across the soft X-ray band demonstrate SXI’s capability to act as a solar wind monitor. This capability is particularly valuable given the lack of reliable near-Earth heavy ion data since the degradation of the solar wind ion spectrometer onboard the Advanced Composition Explorer in 2011.