Multi‐point measurements on kinetic scales through Earth's magnetosheath have revealed a spectrum of filamentary currents and vortical flows advected with the shocked plasmas outside the magnetopause. The spectral energy density in these structures is correlated with enhanced ion temperatures. Using an empirically derived statistical model based on fluid‐kinetic theory for these structures we demonstrate how they act to scatter magnetosheath ions. Through the combined action of energization in the direction perpendicular to the background magnetic field along chaotic orbits, and pitch‐angle scattering into the parallel direction appreciable ion energization occurs. These dynamics drive heating while generating non‐thermal energetic tails similar to that observed. It is shown how the operation of this process depends on the field topology with deviations from planar form and counter‐propagation required to drive significant energization. This process will modulate ion anisotropies through the magnetosheath independent of both adiabatic effects and the action of anisotropy instabilities.
We analyze multipoint measurements in magnetosheath plasmas, just upstream of the Earth's magnetopause, to investigate the morphology of the turbulent fields and coincident 3‐D ion distributions observed. Using interferometric and generalized wave polarization analyses, we show how the fields comprise a multiscale spectrum of Alfvénic structures composed of flow shears and vortices, and current sheets and filaments advected over the spacecraft with the magnetosheath flow. It is shown how these features are correlated with intervals of enhanced ion energy, temperature anisotropy, and impulsive variations in the agyrotropy of ion velocity space distributions. It is demonstrated that the observed variation in ion properties is inconsistent with an adiabatic response but is instead correlated with the spectral energy density of nonplanar structures at ion gyroradii scales. The capacity of these field structures to scatter ions is considered.
more » « less- NSF-PAR ID:
- 10375413
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 47
- Issue:
- 22
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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