Turbulence and Intermittency Driven By Instabilities of the Heliospheric Jets

Abstract The shape and structure of the heliosphere remain under debate, particularly regarding the formation of heliospheric jets and the existence of an open heliotail. Plasma instabilities and turbulent-like dynamics may provide key insights into these unresolved questions. In this work, we use long-term magnetohydrodynamic (MHD) simulations to further investigate the coupled evolution of Rayleigh–Taylor (RT) and Kelvin–Helmholtz (KH) instabilities in the heliosphere and explore their roles in generating and shaping turbulent-like fluctuations in the heliosheath (HS). The results reveal distinct scale-dependent regimes that evolve with the instabilities. The power spectral density (PSD) of magnetic field fluctuation exhibits an approximately k −1 scaling at scales ≳40 au, a steeper scaling close to k −8/3 at intermediate scales of 15–40 au, and a gradual transition toward a Kolmogorov-like k −5/3 scaling at smaller scales of 6–15 au. The intermediate-scale fluctuations remain influenced by instability-driven coherent structures, whereas increasingly turbulent-like characteristics emerge toward smaller scales. The flatness remains near the Gaussian baseline ( F = 3) at large scales but increases above 3 at smaller scales, indicating the emergence of intermittency. The long-term evolution further shows that enhanced flatness and spectral steepening are correlated with recurrent HS instability cycles. These results suggest that the HS exhibits instability-modulated, turbulent-like dynamics, in which large-scale RT/KH-driven coherent structures recurrently evolve and fragment into increasingly complex fluctuations at smaller scales, providing a possible pathway for energy redistribution across spatial scales.