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Abstract: The shape and structure of the heliosphere remain debated, with recent studies suggesting a compact, split­tail configuration (Opher et al. 2015, 2020; Drake et al. 2015). This structure arises from magnetic confinement, which drives north and south heliospheric jets (Opher et al. 2015). Instabilities play a crucial role in shaping the large-scale structure of the heliosphere, particularly in its tail region. Opher et al. (2021) showed that ion-neutral coupling drives Rayleigh-Taylor (RT) instabilities in the heliosheath.
Using global 3D MHD simulations, we identify a low-speed solar wind region formed by charge exchange and magnetic tension, which promotes shear flows and triggers Kelvin-Helmholtz (KH) instabilities with growth timescales of 5-7 years (Ma et al. 2025). We also find that RT and KH instabilities co-evolve cyclically-initially growing together (~4.2 years) before KH modes dominate downstream (~12.9 years). By revealing the periodic and coupled nature of these instabilities, our work provides new insight into the dynamic processes that govern the structure of the outer heliosphere and its interaction with the local interstellar environment. Hosted by Professor Muni Zhou 

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