Jiang, W; Li, H; Liu, X; Verscharen, D; Wang, C; (2023) Statistical Properties of Plateau-Like Turbulence Spectra in the Martian Magnetosheath: MAVEN Observations. Journal of Geophysical Research: Space Physics , 128 (1) , Article e2022JA030874. 10.1029/2022JA030874.

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Abstract

The Martian magnetosheath provides us with a natural laboratory to study plasma turbulence in the presence of pickup ions and locally generated instabilities. Unlike the typical magnetic-field spectra with a single spectral scaling at magnetohydrodynamics (MHD) scales in Earth's magnetosheath, the magnetic-field spectra in the Martian magnetosheath during 4 years of Mars Atmosphere and Volatile EvolutioN observations frequently present an additional spectral break-point with a shallow slope at MHD scales which we define as a plateau-like spectral feature. The average occurrence rate of plateau-like magnetic-field spectra is 56.6% of our measurement intervals. At moderate pick-up angles, the occurrence rate increases to a maximum of ∼70.0%. Furthermore, we present a positive correlation with the local ion density and anti-correlations with the local βi and the solar Extreme Ultra Violet irradiance. A similar occurrence rate in the quasi-perpendicular and the quasi-parallel magnetosheath (60.1% vs. 52.9%) indicates that the plateau-like spectra are more likely formed locally than in the upstream solar wind. Our results suggest that energy injection from pickup ion driven micro-instabilities, for example, in the form of proton cyclotron waves, has insufficient time to evolve into a fully developed cascade in such a confined space like the Martian magnetosheath.

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