Nature of Electrostatic Fluctuations in the Terrestrial Magnetosheath

Silvia Perri*, Denise Perrone, Owen Roberts, Adriana Settino, Emilya Yordanova, Luca Sorriso-Valvo, Pierluigi Veltri, Francesco Valentini

*Corresponding author for this work

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Abstract

The high cadence plasma, electric, and magnetic field measurements by the Magnetospheric MultiScale spacecraft allow us to explore the near-Earth space plasma with an unprecedented time and spatial resolution, resolving electron-scale structures that naturally emerge from plasma complex dynamics. The formation of small-scale turbulent features is often associated to structured, non-Maxwellian particle velocity distribution functions that are not at thermodynamic equilibrium. Using measurements in the terrestrial magnetosheath, this study focuses on regions presenting bumps in the power spectral density of the parallel electric field at subproton scales. Correspondingly, it is found that the ion velocity distribution functions exhibit beam-like features at nearly the local ion thermal speed. Ion-cyclotron waves in the ion-scale range are frequently observed at the same locations. These observations, supported by numerical simulations, are consistent with the generation of ion-bulk waves that propagate at the ion thermal speed. This represents a new branch of efficient energy transfer at small scales, which may be relevant to weakly collisional astrophysical plasmas.

Original languageEnglish
Article number75
Number of pages8
JournalAstrophysical Journal
Volume919
Issue number2
Early online date28 Sept 2021
DOIs
Publication statusPublished - 01 Oct 2021
Externally publishedYes

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