Ion‐Scale Wave Properties and Enhanced Ion Heating Across the Low‐Latitude Boundary Layer During Kelvin‐Helmholtz Instability

• Published in: Journal of geophysical research. Space physics 2017-11, Vol.122 (11), p.11,128-11,153
• Main Authors: Moore, T. W., Nykyri, K., Dimmock, A. P.
• Format: Article
• Language: English
• Subjects: Asymmetry; Boundary layer stability; Boundary layers; Earth magnetosphere; Free energy; Heating; Inertia; Instability; Interplanetary magnetic field; Intervals; Ion heating; Ions; Kelvin-Helmholtz instability; Magnetic fields; Magnetic properties; Magnetopause; Magnetosheath; Magnetosphere; Magnetotail plasma; Magnetotails; multiscale; Plasma; Solar wind; Statistical analysis; Wave generation; Wave propagation
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1002/2017JA024591

In the Earth's magnetosphere, the magnetotail plasma sheet ions are much hotter than in the shocked solar wind. On the dawn sector, the cold‐component ions are more abundant and hotter by 30–40% when compared to the dusk sector. Recent statistical studies of the flank magnetopause and magnetosheath have shown that the level of temperature asymmetry of the magnetosheath is unable to account for this, so additional physical mechanisms must be at play, either at the magnetopause or plasma sheet that contributes to this asymmetry. In this study, we perform a statistical analysis on the ion‐scale wave properties in the three main plasma regimes common to flank magnetopause boundary crossings when the boundary is unstable to Kelvin‐Helmholtz instability (KHI): hot and tenuous magnetospheric, cold and dense magnetosheath, and mixed (Hasegawa et al., 2004). These statistics of ion‐scale wave properties are compared to observations of fast magnetosonic wave modes that have recently been linked to Kelvin‐Helmholtz (KH) vortex centered ion heating (Moore et al., 2016). The statistical analysis shows that during KH events there is enhanced nonadiabatic heating calculated during ion scale wave intervals when compared to non‐KH events. This suggests that during KH events there is more free energy for ion‐scale wave generation, which in turn can heat ions more effectively when compared to cases when KH waves are absent. This may contribute to the dawn favored temperature asymmetry of the plasma sheet; recent studies suggest KH waves favor the dawn flank during Parker‐Spiral interplanetary magnetic field. Key Points Obliquely propagating waves have more power in the MSP‐like plasma regions when KHI is present Strong nonadiabatic heating associated with ion‐scale wave activity is enhanced during intervals of Kelvin‐Helmholtz instability The enhanced ion‐scale wave activity and ion heating during KHI may explain the temperature asymmetry of cold component plasma sheet ions