On the 1/f Spectrum in the Solar Wind and Its Connection with Magnetic Compressibility

Matteini, Lorenzo; Stansby, David; Horbury, T. S.; Chen, C. H. K.

doi:10.3847/2041-8213/aaf573

Cited by 65 publications

(74 citation statements)

References 35 publications

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“…The distributions are broadly more Gaussian in character and shift towards larger δB/B values with increasing timescale. These fluctuation scaling trends are a well established feature of the solar wind plasma (Sorriso-Valvo et al 2001) and have recently been demonstrated with δB/B distributions in a similar fashion to Figure 2 (Chen et al 2015;Matteini et al 2018).…”

Section: Magnetic Fluctuationssupporting

confidence: 76%

Radial Evolution of Magnetic Field Fluctuations in an Interplanetary Coronal Mass Ejection Sheath

Good

Ala‐Lahti

Palmerio

et al. 2020

ApJ

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The sheaths of compressed solar wind that precede interplanetary coronal mass ejections (ICMEs) commonly display large-amplitude magnetic field fluctuations. As ICMEs propagate radially from the Sun, the properties of these fluctuations may evolve significantly. We have analyzed magnetic field fluctuations in an ICME sheath observed by MESSENGER at 0.47 au and subsequently by STEREO-B at 1.08 au while the spacecraft were close to radial alignment. Radial changes in fluctuation amplitude, compressibility, inertial-range spectral slope, permutation entropy, Jensen-Shannon complexity, and planar structuring are characterized. These changes are discussed in relation to the evolving turbulent properties of the upstream solar wind, the shock bounding the front of the sheath changing from a quasi-parallel to quasi-perpendicular geometry, and the development of complex structures in the sheath plasma.

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Section: Magnetic Fluctuationssupporting

confidence: 76%

Radial Evolution of Magnetic Field Fluctuations in an Interplanetary Coronal Mass Ejection Sheath

Good

Ala‐Lahti

Palmerio

et al. 2020

ApJ

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“…As already recalled before, Matteini et al (2018) suggested that the 1/ f scaling observed in fast wind magnetic field might be the consequence of the large-scale saturation of the fluctuations. In this perspective, the amplitude of the fluctuations would be limited by the magnitude of the local magnetic field.…”

Section: Discussionmentioning

confidence: 62%

“…At this point, we checked whether a saturation effect of the fluctuations, similar to that suggested by Matteini et al (2018) for the fast Alfvénic wind, could also play a role in the slow wind spectral break. Thus, in order to explore this possibility, differently from Matteini et al (2018) who used first-order structure functions, we estimated the amplitude of each Fourier mode using the simple relation that binds together the power of a given fluctuation and the amplitude of the fluctuation δB( f ), by means of the Fourier power spectral density S ( f ), namely δB( f ) = 2 f S ( f ). These values were successively normalized to the corresponding local magnetic field average within each interval |B| , and are shown in Fig.…”

Section: Discussionmentioning

confidence: 90%

The low-frequency break observed in the slow solar wind magnetic spectra

Bruno

Telloni

Sorriso‐Valvo

et al. 2019

A&A

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Fluctuations of solar wind magnetic field and plasma parameters exhibit a typical turbulence power spectrum with a spectral index ranging between ∼ 5/3 and ∼ 3/2. In particular, at 1 AU, the magnetic field spectrum, observed within fast corotating streams, also shows a clear steepening for frequencies higher than the typical proton scales, of the order of ∼ 3 × 10 −1 Hz, and a flattening towards 1/ f at frequencies lower than ∼ 10 −3 Hz. However, the current literature reports observations of the low-frequency break only for fast streams. Slow streams, as observed to date, have not shown a clear break, and this has commonly been attributed to slow wind intervals not being long enough. Actually, because of the longer transit time from the Sun, slow wind turbulence would be older and the frequency break would be shifted to lower frequencies with respect to fast wind. Based on this hypothesis, we performed a careful search for long-lasting slow wind intervals throughout 12 years of Wind satellite measurements. Our search, based on stringent requirements not only on wind speed but also on the level of magnetic compressibility and Alfvénicity of the turbulent fluctuations, yielded 48 slow wind streams lasting longer than 7 days. This result allowed us to extend our study to frequencies sufficiently low and, for the first time in the literature, we are able to show that the 1/ f magnetic spectral scaling is also present in the slow solar wind, provided the interval is long enough. However, this is not the case for the slow wind velocity spectrum, which keeps the typical Kolmogorov scaling throughout the analysed frequency range. After ruling out the possible role of compressibility and Alfvénicity for the 1/ f scaling, a possible explanation in terms of magnetic amplitude saturation, as recently proposed in the literature, is suggested.

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“…The fluctuations exhibit Alfvénic polarization properties (see Sect. 4.3.1) and B ≈ constant (Matteini et al, 2018;Bruno et al, 2019).…”

Section: Phenomenology Of Plasma Turbulence In the Solar Windmentioning

confidence: 96%

The multi-scale nature of the solar wind

Verscharen¹,

Klein²,

Maruca³

2019

Living Rev Sol Phys

296

280

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The solar wind is a magnetized plasma and as such exhibits collective plasma behavior associated with its characteristic spatial and temporal scales. The characteristic length scales include the size of the heliosphere, the collisional mean free paths of all species, their inertial lengths, their gyration radii, and their Debye lengths. The characteristic timescales include the expansion time, the collision times, and the periods associated with gyration, waves, and oscillations. We review the past and present research into the multi-scale nature of the solar wind based on in-situ spacecraft measurements and plasma theory. We emphasize that couplings of processes across scales are important for the global dynamics and thermodynamics of the solar wind. We describe methods to measure in-situ properties of particles and fields. We then discuss the role of expansion effects, non-equilibrium distribution functions, collisions,

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On the 1/f Spectrum in the Solar Wind and Its Connection with Magnetic Compressibility

Cited by 65 publications

References 35 publications

Radial Evolution of Magnetic Field Fluctuations in an Interplanetary Coronal Mass Ejection Sheath

Radial Evolution of Magnetic Field Fluctuations in an Interplanetary Coronal Mass Ejection Sheath

The low-frequency break observed in the slow solar wind magnetic spectra

The multi-scale nature of the solar wind

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