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New Insights into the Nature of Turbulence in the Earth's Magnetosheath Using Magnetospheric MultiScale Mission Data

  • Breuillard, Hugo
  • Matteini, L.
  • Argall, M. R.
  • Sahraoui, Fouad
  • Andriopoulou, M.
  • Le Contel, Olivier
  • Retinò, Alessandro
  • Mirioni, Laurent
  • Huang, S. Y.
  • Gershman, D. J.
  • Ergun, R. E.
  • Wilder, F. D.
  • Goodrich, K. A.
  • Ahmadi, N.
  • Yordanova, E.
  • Vaivads, A.
  • Turner, D. L.
  • Khotyaintsev, Y. V.
  • Graham, D. B.
  • Lindqvist, P.-A.
  • And 14 more
Publication Date
Jan 01, 2018
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The Earth's magnetosheath, which is characterized by highly turbulent fluctuations, is usually divided into two regions of different properties as a function of the angle between the interplanetary magnetic field and the shock normal. In this study, we make use of high-time resolution instruments on board the Magnetospheric MultiScale spacecraft to determine and compare the properties of subsolar magnetosheath turbulence in both regions, i.e., downstream of the quasi-parallel and quasi-perpendicular bow shocks. In particular, we take advantage of the unprecedented temporal resolution of the Fast Plasma Investigation instrument to show the density fluctuations down to sub-ion scales for the first time. We show that the nature of turbulence is highly compressible down to electron scales, particularly in the quasi-parallel magnetosheath. In this region, the magnetic turbulence also shows an inertial (Kolmogorov-like) range, indicating that the fluctuations are not formed locally, in contrast with the quasi-perpendicular magnetosheath. We also show that the electromagnetic turbulence is dominated by electric fluctuations at sub-ion scales (f > 1 Hz) and that magnetic and electric spectra steepen at the largest-electron scale. The latter indicates a change in the nature of turbulence at electron scales. Finally, we show that the electric fluctuations around the electron gyrofrequency are mostly parallel in the quasi-perpendicular magnetosheath, where intense whistlers are observed. This result suggests that energy dissipation, plasma heating, and acceleration might be driven by intense electrostatic parallel structures/waves, which can be linked to whistler waves.

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