Exploring the response of planetary magnetospheres to intense space weather events

Extreme Space Weather (SWE) events have a crucial role in shaping the dynamics of Earth's magnetospheric boundary layer. Under such conditions, several plasma processes can be triggered, including the Kelvin-Helmholtz instability (KHI). This instability arises from the velocity shear at the boundary of two regions: the nearly stagnant magnetosphere (MSP) and the anti-sunward streaming magnetosheath (MSH).KHI can grow into finite-amplitude Kelvin–Helmholtz waves (KHWs), which may subsequently roll-up into large-scale vortices (KHVs). These vortices can twist magnetic field lines and trigger vortex-induced tearing mode instability (TMI). In the context of planetary magnetospheric dynamics, such instabilities are fundamental because they (i) drive substantial mass, energy, and momentum transport from the MSH into the MSP; (ii) generate ultra-low-frequency magnetospheric waves; and (iii) drive field-aligned currents coupling to the ionosphere.In this work, we analyze two SWE events that occurred in January and November 2025, during which the Sun produced some of the strongest flares of Solar Cycle 25, associated with Earth-directed coronal mass ejections (CMEs). Our study combines in-situ magnetospheric observations from MMS and THEMIS with ionospheric measurements from Swarm. Furthermore, we employ our two-dimensional magnetohydrodynamic (MHD) model (Ivanovski et al. 2011; Biasiotti et al. 2024) to characterize the flow dynamics within the magnetopause mixing layer in the fluid limit.Finally, we analyze predictions of solar activity for May 2039, the expected operational window of the proposed Plasma Observatory (PO) mission, to identify analogue intervals representative of the SWE conditions likely to be encountered by PO. We also examine the orbits of THEMIS, MMS, and Cluster to search for comparable magnetopause crossings. Our results indicate that the orbital configuration of PO would enable continuous monitoring of the dawnside magnetopause for 10-12 days, allowing the full evolution of KH vortices and their interaction with TMI to be captured. This represents a unique capability compared with current missions, which observe such processes only during brief and sporadic crossings.  This research has been carried out within the framework of the Space It Up project funded by the Italian Space Agency, ASI, and the Ministry of University and Research, MUR, under contract n. 2024-5-E.0 - CUP n. I53D24000060005.