Speaker
Description
We examine the propagation, interaction, and turbulence properties of a multi-CME sequence erupted between 9–11 November 2025, using multi-spacecraft in situ observations from Aditya-L1 (MAG, ASPEX), WIND (SWE), MMS (FGM), and Solar Orbiter (MAG, EPD; positioned at 0.83 AU, 13.5° inclination), supplemented by ground-based neutron monitor data. X1.7 and X1.2 flares on 9–10 November (07:36 and 09:48 UT) produced CMEs with speeds of 625 and 1644 km/s, respectively; the faster ejecta overtook the preceding one, forming a complex merged structure whose shock arrived at L1 at ~23:48 UT on 11 November, driving an intense geomagnetic storm (Dst_min = −217 nT). Quasi-perpendicular shock parameters were derived from peak ion flux enhancements (Aditya-L1/ASPEX, Solar Orbiter/EPD) and triaxial magnetic field discontinuities (Aditya-L1/MAG, Solar Orbiter/MAG), followed by a turbulent sheath. Velocity, density, temperature, energetic-ion, and IMF signatures indicate clear ICME-ICME interaction. A subsequent X5.1 flare (10:04 UT, AR 14274) generated a 1845 km/s CME whose leading edge overtook the trailing magnetic cloud of the 10 November ejecta, producing an ICME-in-sheath configuration with compressed, turbulent plasma and anomalous fluctuations observed between 10:00–12:00 UT on 12 November. MMS-derived PSD analysis yields a kinetic-scale spectral index of ≈−2.602, intermediate between KAW- and whistler-type turbulence, indicating enhanced dissipation. Neutron monitor data confirm GLE #77, exhibiting a rare double-peak, anisotropic profile. ENLIL simulations corroborate the merged-ejecta formation and subsequent interaction with the preconditioned heliosphere, elucidating shock-driven particle acceleration mechanisms relevant to SEP generation.