The Plasma Observatory Synergies and Additional Science Working Group

The main aim of the ESA Class-M7 Plasma Observatory (PO) mission currently in Phase A, is to explore the multiscale physics governing energy transfer and particle energization in near-Earth space plasmas. Flying a constellation of seven spacecraft in a double nested tetrahedral configuration, PO will deliver simultaneous measurements of fields, waves, and particles across ion, sub-ion, and MHD scales in various regions of the near-Earth space, within 7 to 13 Earth radii. While the mission core science focuses on regions such as the bow shock, magnetosheath, magnetopause, and plasma sheet, the orbital design naturally enables extensive coverage of additional regions, including the inner magnetosphere, the flanks of the magnetopause, and the ambient solar wind. The Synergies and Additional Science Working Group investigates the scientific opportunities enabled by PO observations beyond the primary science regions and aims to broaden the mission scientific impact through cross-disciplinary synergies. The solar-wind-driven magnetosphere is a highly dynamic system in which key processes can only be resolved through multipoint, multiscale observations.With seven-point measurements, PO will allow the multiscale characterization of M-I coupling and plasma sources of both solar wind and ionospheric origin under varying geomagnetic conditions. In the inner magnetosphere, PO will address fundamental questions on wave propagation and wave-particle interactions at the edge of the outer radiation belt. Multipoint observations of ULF, EMIC, chorus, and whistler-mode waves will enable direct in-situ identification of acceleration, transport, and loss processes of energetic particles. PO will also resolve the multiscale structure and evolution of plasmaspheric plumes of cold plasma and assess their role in wave generation and radiation belt dynamics. At the flank magnetopause and in the upstream solar wind, PO will probe the coupling between large-scale plasma dynamics, turbulence, and kinetic dissipation. Simultaneous measurements at multiple scales will allow detailed investigations of Kelvin-Helmholtz instability, reconnection, plasma mixing, and turbulent energy transfer, as well as accessing the fine structure of solar wind transients that control mass and energy input into the magnetosphere.PO will further enable strong synergies with other heliophysics missions, laboratory plasma experiments, and space weather research. PO multiscale observations will improve constraints on M-I coupling currents, geomagnetically induced currents, and CME-driven disturbances, while providing a unique space-based counterpart to laboratory reconnection experiments. This contribution summarizes recent progress within the Synergies and Additional Science Working Group and outlines future perspectives supporting PO during Phase A.