Abstract
It is currently believed that the turbulent fluctuations pervade the outermost heliosphere. Turbulence, magnetic reconnection, and their link may be responsible for magnetic energy conversion in these regions. The governing mechanisms of such anisotropic and compressible magnetic turbulence in the inner heliosheath (IHS) and in the local interstellar medium (LISM) still lack a thorough description. The present literature mainly concerns large scales which are not representative of the inertial-cascade dynamics of turbulence. Moreover, lack of broadband spectral analysis makes the IHS dynamics critically understudied. Our recent study [1] shows that 48 s magnetic-field data from the Voyager mission are appropriate for a spectral analysis over a frequency range of six decades, from 5 × 10−8 Hz to 10−2 Hz. Here, focusing on the Voyager 2 observation interval from 2013.824 to 2016.0, we describe the structure of turbulence in a sector zone of the IHS. A spectral break around 7 × 10−7 Hz (magnetic structures with size ℓ ≈ 1.3 Astronomical Units) separates the energy-injection regime from the inertial-cascade regime of turbulence. A second scale is observed around 6 × 10−5 Hz (ℓ ≈ 0.017 AU) and corresponds to a peak of compressibility and intermittency of fluctuations.
Highlights
The Voyagers (V1, V2) are the only operating spacecraft providing us with in situ data from the outermost part of heliosphere
This study extends our recent work [1], where a spectral analysis of Voyager 1 (V1) and V2 data magnetic field data was performed for several inner heliosheath (IHS) and local interstellar medium (LISM) periods
The red, green and blue curves stand for δB, δB⊥1, δB⊥2, respectively, while the total magnetic energy Em(f ) = P [B ] + P [B⊥1] + P [B⊥2] is represented in black
Summary
The Voyagers (V1, V2) are the only operating spacecraft providing us with in situ data from the outermost part of heliosphere. We investigate the spectral properties of magnetic field fluctuations in the energy-injection and inertial-cascade ranges of turbulence, with focus on the variance anisotropy, the presence of compressible modes, and high-order multi-scale statistics.
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