Magnetic reconnection and Kelvin–Helmholtz instabilities at the Earth's magnetopause

Abstract

Kelvin-Helmholtz instability (KHI), driven by the velocity inhomogeneity at Earth's magnetopause, has been shown to play a major role in mixing the magnetospheric and the solar wind plasma during northward periods. In fact, when the magnetospheric and interplanetary magnetic fields are mostly perpendicular to the equatorial plane, KHI can develop at a low latitude without being significantly inhibited by the magnetic tension. In contrast, at a high latitude, the more complex magnetic configuration is believed to totally stabilize the instability. This intrinsic 3D dynamics is investigated in a simplified geometry showing that KHI is able to kink the magnetic field lines at a mid-latitude and to create current layers where magnetic reconnection spontaneously develops. It is shown that a mid-latitude reconnection is able to change the global topology of the magnetic field and to connect interplanetary field lines to the Earth's cups, allowing the solar wind to directly enter the magnetosphere.

Asymmetric Kelvin‐Helmholtz propagation at Saturn's dayside magnetopause

“…But a small B z component will increase significantly for a polar‐flattened magnetosphere [ Desroche et al , ]. For southward IMF conditions [ Faganello et al , ], it is clear that magnetic reconnection is switched off on the prenoon side, where the transition layer is wide and there are no antiparallel magnetic field components. In contrast, the slowly growing KH modes on the duskside are likely to locally twist magnetic flux, which leads to a pair of high‐latitude magnetic reconnection regions in three dimensions (e.g., green patchy in Figure ).…”

Turbulent plasma transport across the Earth's low‐latitude boundary layer

“…This may be due to the local setup employed in this letter. In particular, there are a variety of other processes which may influence the entropy profile across the boundary layer, such as the midlatitude vortex‐induced reconnection [ Takagi et al , ; Faganello et al , , ] or the mode conversion into the kinetic Alfvén waves [ Chaston et al , ]. Investigating the coupling among all of these local and semiglobal processes as well as other global processes such as the high‐latitude reconnection is an important direction for future research, which would require high‐resolution global simulations.…”

Plasma transport driven by the Rayleigh‐Taylor instability

“…High‐latitude reconnection in our model is component magnetic reconnection in three dimensions, being difficult to describe from a topological view. A good example is the three‐dimensional Kelvin‐Helmholtz instability [see Faganello et al , , Figure ]. In this study we use three different methods to demonstrate the presence of high‐latitude reconnection, i.e., estimating the field‐aligned potential difference, ϕ ; examining the frozen‐in condition by the definition; and examining the change of the flux tube content and flux tube entropy.…”