Magnetic turbulence spectra and intermittency in the heliosheath and in the local interstellar medium

Abstract

The understanding of inertial-scale dynamics in the heliosheath is not yet thorough. Magnetic field fluctuations across the inner heliosheath (IHS) and the local interstellar medium (LISM) are here considered to provide accurate and highly resolved statistics over different plasma conditions between 88 and 136 au. By using the unique in situ 48 s measurements from the Voyager Interstellar Mission, we investigate different fluctuation regimes at the magnetohydrodynamic (MHD) scales, down to the MHD-to-kinetic transition. We focus on a range of scales exceeding five frequency decades (5 x 10-8 < f < 10-2 Hz), which is unprecedented in literature analysis. A set of magnetic field data for eight intervals in the IHS, in both unipolar and sector regions, and four intervals in the LISM is used for the analysis. Results are set forth in terms of the power spectral density, spectral compressibility, structure functions, and intermittency of magnetic field increments. In the heliosheath, we identify the energy-injection regime displaying a ~1/f energy decay, and the inertial-cascade regime. Here, the power spectrum is anisotropic and dominated by compressive modes, with intermittency that can reach kurtosis values of up to 10. In the interstellar medium the structure of turbulence is anisotropic as well, with transverse fluctuations clearly prevailing after 2015 May. Here, we show that intermittent features occur only at scales smaller than 10-6 Hz.

32 pages, 12 figures

References in corpus (12)

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Cited by in corpus (12)

• The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere
• Critical Balance and the Physics of MHD Turbulence
• Dissipation measures in weakly-collisional plasmas
• Turbulence in the outer heliosphere
• A Statistical Study of the Compressible Energy Cascade Rate in Solar Wind Turbulence: Parker Solar Probe Observations
• On the Generation of Compressible Mirror-mode Fluctuations in the Inner Heliosheath
• Exploring the intermittency of magnetohydrodynamic turbulence by synchrotron polarization radiation
• The structure of magnetic turbulence in the heliosheath region observed by Voyager 2 at 106 AU
• Exploring the potential of neural networks to predict statistics of solar wind turbulence
• De-Biasing Structure Function Estimates From Sparse Time Series of the Solar Wind: A Data-Driven Approach
• Direct power spectral density estimation from structure functions without Fourier transforms
• Probability Density Functions in Homogeneous and Isotropic Magneto-Hydrodynamic Turbulence