Asymmetric Kelvin‐Helmholtz Instability at Jupiter's Magnetopause Boundary: Implications for Corotation‐Dominated Systems

Abstract

The multifluid Lyon‐Fedder‐Mobarry (MFLFM) global magnetosphere model is used to study the interactions between solar wind and rapidly rotating, internally driven Jupiter magnetosphere. The MFLFM model is the first global simulation of Jupiter magnetosphere that captures the Kelvin‐Helmholtz instability (KHI) in the critically important subsolar region. Observations indicate that Kelvin‐Helmholtz vortices are found predominantly in the dusk sector. Our simulations explain that this distribution is driven by the growth of KHI modes in the prenoon and subsolar region (e.g., >10 local time) that are advected by magnetospheric flows to the dusk sector. The period of density fluctuations at the dusk terminator flank (18 magnetic local time, MLT) is roughly 1.4 h compared with 7.2 h at the dawn flank (6 MLT). Although the simulations are only performed using parameters of the Jupiter's magnetosphere, the results may also have implications for solar wind‐magnetosphere interactions at other corotation‐dominated systems such as Saturn. For instance, the simulated average azimuthal speed of magnetosheath flows exhibit significant dawn‐dusk asymmetry, consistent with recent observations at Saturn. The results are particularly relevant for the ongoing Juno mission and the analysis of dawnside magnetopause boundary crossings for other planetary missions.

Cassini/MIMI Observations on the Dungey Cycle Reconnection and Kelvin‐Helmholtz Instability in Saturn's Magnetosphere

“…The increasing radial distribution of He ++ relative abundance, peaking at ∼10% at large distances, ∼40-55 Rs toward the dawn sector, suggests that local reconnection inside KHI vortices leads to mixing of plasma in the dawn sector and directed toward the tail. The KHI as a possible entry mechanism is also supported by recent Cassini observations (e.g., Delamere et al, 2011Delamere et al, , 2013Masters et al, 2009Masters et al, , 2010Masters et al, , 2012Wilson et al, 2012) and simulations (e.g., Ma et al, 2015;Zhang et al, 2018) showing asymmetric KHI wave properties between dusk and dawn.…”

A More Viscous‐Like Solar Wind Interaction With All the Giant Planets

“…This is not only due to higher magnetospheric plasma density but also because the contribution of appreciable plasma pressure to total pressure balance with the solar wind leads to a weaker outer magnetospheric magnetic field, offset to some extent by formation of cushion regions (e.g., Went et al, 2011). We assert that corotation of magnetospheric plasma and the draped IMF twisting that can occur at these polar-flattened magnetospheres (e.g., Desroche et al, 2012;Erkaev et al, 1996) are effects that primarily change the pattern of flow and magnetic shears across the magnetopause, producing asymmetries (Zhang et al, 2018) but not affecting our conclusion.…”

Identifying Active Kelvin–Helmholtz Vortices on Saturn's Magnetopause Boundary

“…The dawn magnetopause has large KH growth rates so the boundary quickly diffuses into a broad layer with an uncertain lifetime. The dusk magnetopause is mostly structured by nonevolving KH waves advecting downtail rather than actively rolling‐up (Ma et al, ; Zhang et al, ). We summarize our findings as follows: Reversed flows near Saturn's magnetopause indicate active KH vortices % of the time prenoon and % postnoon.…”