Coherent Structures at Ion Scales in Fast Solar Wind: Cluster Observations

Perrone, D.; Alexandrova, Olga; Roberts, Owen; Lion, Sonny; Lacombe, Catherine; Walsh, A. P.; Maksimović, M.; Zouganelis, I.

doi:10.3847/1538-4357/aa9022

Cited by 76 publications

(114 citation statements)

References 90 publications

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“…Recently, kinetic Alfvén waves (KAWs) have been invoked to explain the morphology of the spectrum at ion kinetic scales in the solar wind (e.g., He et al, ; Podesta, ; Sahraoui et al, ; Salem et al, ; Telloni et al, ) and in the magnetosheath (Chen & Boldyrev, ). Multispacecraft observations of solar wind plasma at ion scales often reveal slowly propagating fluctuations in the plasma frame with low intrinsic frequencies ω pla ∼0 (e.g., Perrone et al, ; O. W. Roberts et al, , ). This result has been interpreted either as KAW turbulence (Sahraoui et al, ), coherent structures which are mostly advected in by the bulk flow (Perrone et al, , ; O. W. Roberts et al, ), a mixture of KAWs and advected structures (Perschke et al, ; O. W. Roberts et al, , ), or nonlinear fluctuations (Perschke et al, ; O. W. Roberts, Narita, Li, et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…Multispacecraft observations of solar wind plasma at ion scales often reveal slowly propagating fluctuations in the plasma frame with low intrinsic frequencies ω pla ∼0 (e.g., Perrone et al, ; O. W. Roberts et al, , ). This result has been interpreted either as KAW turbulence (Sahraoui et al, ), coherent structures which are mostly advected in by the bulk flow (Perrone et al, , ; O. W. Roberts et al, ), a mixture of KAWs and advected structures (Perschke et al, ; O. W. Roberts et al, , ), or nonlinear fluctuations (Perschke et al, ; O. W. Roberts, Narita, Li, et al, ). Until recently, the role of kinetic slow waves (KSWs) have largely been ignored as it is heavily damped for the typical plasma parameters of the solar wind (Barnes, ; Narita & Marsch, ).…”

Section: Introductionmentioning

confidence: 99%

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Ion‐Scale Kinetic Alfvén Turbulence: MMS Measurements of the Alfvén Ratio in the Magnetosheath

Roberts

Toledo‐Redondo

Perrone

et al. 2018

Geophysical Research Letters

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Turbulence in the Earth's magnetosheath at ion kinetic scales is investigated with the magnetospheric multiscale spacecraft. Several possibilities in the wave paradigm have been invoked to explain plasma turbulence at ion kinetic scales such as kinetic Alfvén, slow, or magnetosonic waves. To differentiate between these different plasma waves is a challenging task, especially since some waves, in particular, kinetic slow waves and kinetic Alfvén waves, share some properties making the possibility to distinguishing between them very difficult. Using the excellent time resolution data set provided from both the fluxgate magnetometer and the Fast Plasma Instrument, the ratio of trace velocity fluctuations to the magnetic fluctuations (in Alfvén units), which is termed the Alfvén ratio, can be calculated down to ion kinetic scales. Comparison of the measured Alfvén ratio is performed with respect to the expectation from two‐fluid magnetohydrodynamic theory for the kinetic slow wave and kinetic Alfvén wave. Moreover, the plasma data also allow normalized fluctuation amplitudes of density and magnetic field to be compared differentiating between magnetosonic‐like and kinetic Alfvén‐like turbulence. Using these two different ratios, we can rule out that the fluctuations at ion scales are dominated by magnetosonic‐like fluctuations or kinetic slow‐like fluctuations and show that they are consistent with kinetic Alfvén‐like fluctuations. This suggests that in the wave paradigm, heating in the direction of the parallel magnetic field is predominantly by the Landau damping of the kinetic Alfvén wave.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ion‐Scale Kinetic Alfvén Turbulence: MMS Measurements of the Alfvén Ratio in the Magnetosheath

Roberts

Toledo‐Redondo

Perrone

et al. 2018

Geophysical Research Letters

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“…Schematic of the THEMIS mission (credit: NASA/ESA). Roberts et al, 2016;Perrone et al, 2016Perrone et al, , 2017. In addition, some results on very high-resolution data on electron scales have recently been provided by the Magnetospheric Multiscale (MMS) mission (Yordanova et al, 2016;Chasapis et al, 2017).…”

Section: Magnetosheath Turbulencementioning

confidence: 99%

Intermittent turbulence in the heliosheath and the magnetosheath plasmas based on Voyager and THEMIS data

Macek

Wawrzaszek

Kucharuk

2018

Nonlin. Processes Geophys.

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Abstract. Turbulence is complex behavior that is ubiquitous in space, including the environments of the heliosphere and the magnetosphere. Our studies on solar wind turbulence including the heliosheath, and even at the heliospheric boundaries, also beyond the ecliptic plane, have shown that turbulence is intermittent in the entire heliosphere. As is known, turbulence in space plasmas often exhibits substantial deviations from normal Gaussian distributions. Therefore, we analyze the fluctuations of plasma and magnetic field parameters also in the magnetosheath behind the Earth's bow shock. Based on THEMIS observations, we have already suggested that turbulence behind the quasi-perpendicular shock is more intermittent with larger kurtosis than that behind the quasiparallel shocks. Following this study, we would like to present a detailed analysis of intermittent anisotropic turbulence in the magnetosheath depending on various characteristics of plasma behind the bow shock and now also near the magnetopause. In particular, for very high Alfvénic Mach numbers and high plasma beta we have clear non-Gaussian statistics in the directions perpendicular to the magnetic field. On the other hand, for directions parallel to this field the kurtosis is small and the plasma is close to equilibrium. However, the level of intermittency for the outgoing fluctuations seems to be similar to that for the ingoing fluctuations, which is consistent with approximate equipartition of energy between the oppositely propagating Alfvén waves. We hope that the difference in characteristic behavior of these fluctuations in various regions of space plasmas can help to detect some complex structures in space missions in the near future.

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“…Several multi-spacecraft observations of the solar wind have revealed that the fluctuations at proton kinetic scales typically have low intrinsic propagation speeds in the plasma frame. This result has been interpreted as evidence of kinetic Alfvén waves (KAWs) (Sahraoui et al, 2010), as coherent structures which are predominantly advected with the bulk velocity (Perrone et al, 2017), as a combination of KAW turbulence and coherent structures (Roberts et al, 2013(Roberts et al, , 2015, or as nonlinear modes where wave-wave interactions have broadened the dispersion relation diagram (Narita and Motschmann, 2017;Roberts et al, 2017). Kinetic slow waves (KSWs) are the kinetic counterpart of the magnetohydrodynamic (MHD) slow mode when it develops a large perpendicular wave number, and it shares many properties with the KAW, such as a similar dispersion relation and anticorrelated fluctuations in magnetic field and density Narita and Marsch, 2015).…”

Section: Introductionmentioning

confidence: 99%

Multi-scale analysis of compressible fluctuations in the solar wind

Roberts¹,

Narita²,

Escoubet³

2018

Ann. Geophys.

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Abstract. Compressible plasma turbulence is investigated in the fast solar wind at proton kinetic scales by the combined use of electron density and magnetic field measurements. Both the scale-dependent cross-correlation (CC) and the reduced magnetic helicity (σ m ) are used in tandem to determine the properties of the compressible fluctuations at proton kinetic scales. At inertial scales the turbulence is hypothesised to contain a mixture of Alfvénic and slow waves, characterised by weak magnetic helicity and anti-correlation between magnetic field strength B and electron density n e . At proton kinetic scales the observations suggest that the fluctuations have stronger positive magnetic helicities as well as strong anti-correlations within the frequency range studied. These results are interpreted as being characteristic of either counter-propagating kinetic Alfvén wave packets or a mixture of anti-sunward kinetic Alfvén waves along with a component of kinetic slow waves.

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Coherent Structures at Ion Scales in Fast Solar Wind: Cluster Observations

Cited by 76 publications

References 90 publications

Ion‐Scale Kinetic Alfvén Turbulence: MMS Measurements of the Alfvén Ratio in the Magnetosheath

Ion‐Scale Kinetic Alfvén Turbulence: MMS Measurements of the Alfvén Ratio in the Magnetosheath

Intermittent turbulence in the heliosheath and the magnetosheath plasmas based on Voyager and THEMIS data

Multi-scale analysis of compressible fluctuations in the solar wind

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