Abstract: During the increase and maximum phases of the 25th solar cycle, a number of solar proton events (SPE) were observed, some of which were measured by the Liulin-MO instrument onboard the ExoMars Trace Gas Orbiter (TGO) in orbit around Mars. Liulin-MO is a module of FREND instrument on TGO. The results have been published in a series of presentations and articles. In this presentation, we will focus on the effect of the modulation of the flux measured by Liulin-MO, which we consider to be due to the orbital motion of the TGO spacecraft. Rather strong increases in particle fluxes during the SPE on October 28, 2021, February 15, 2022, and May 20, 2024 were considered. Variations in the solar cosmic ray flux were compared with the relative position of Mars, the TGO spacecraft, and the direction of the force line of the interplanetary magnetic field (IMP). Shown is that the flux decreases when the calculated direction of the IMP force line from the Sun is shaded by Mars or by sufficiently thick structural elements of the FREND device and the TGO spacecraft. A possible explanation for the observed effect may be that the distribution of particle arrivals during a SPE is not isotropic in the vicinity of Mars, and the flux of particles coming from directions close to the direction of the IMP field line is noticeably higher than the average level.

Cite: Benghin V. , Drobyshev S. , Semkova J. , Koleva R. , Dachev T. , Shurshakov V. , Krastev K. , Matviichuk Y. , Tomov B. , Bankov N. , Maltchev S. , Mitrofanov I. , Golovin D. , Mokrousov M. , Litvak M. , Lukyanov N.
Modulation of the Particle Flux Detected by the Liulin-MO Instrument During Solar Proton Events Caused by the Orbital Motion of the Exomars TGO Spacecraft Around Mars
17TH INTERNATIONAL WORKSHOP “SOLAR INFLUENCES ON THE MAGNETOSPHERE, IONOSPHERE, AND ATMOSPHERE” 02-06 Jun 2025