The multi-scale nature of the solar wind

Verscharen, Daniel; Klein, K. G.; Maruca, Bennett A.

doi:10.1007/s41116-019-0021-0

Cited by 302 publications

(296 citation statements)

References 709 publications

(792 reference statements)

Supporting

Mentioning

285

Contrasting

Order By: Relevance

“…Departures of particle velocity distributions from local thermodynamic equilibrium in the weakly collisional solar wind are frequently observed (see Marsch 2012 andVerscharen et al 2019 for a review of such measurements) and are associated with wave-particle instabilities, a class of interactions that act to move particle distributions toward equilibrium while simultaneously emitting a variety of plasma waves. A review of the linear and quasilinear theory associated with such instabilities can be found in Gary (1993) and Yoon (2017).…”

Section: Introductionmentioning

confidence: 99%

Alfvénic velocity spikes and rotational flows in the near-Sun solar wind

Kasper¹,

Bale²,

Belcher³

et al. 2019

Nature

370

299

View full text Add to dashboard Cite

Wave-particle instabilities driven by departures from local thermodynamic equilibrium have been conjectured to play a role in governing solar wind dynamics. We calculate the statistical variation of linear stability over a large subset of Helios I and II observations of the fast solar wind using a numerical evaluation of the Nyquist stability criterion, accounting for multiple sources of free energy associated with protons and helium including temperature anisotropies and relative drifts. We find that 88% of the surveyed intervals are linearly unstable. The median growth rate of the unstable modes is within an order of magnitude of the turbulent transfer rate, fast enough to potentially impact the turbulent scale-to-scale energy transfer. This rate does not significantly change with radial distance, though the nature of the unstable modes, and which ion components are responsible for driving the instabilities, does vary. The effect of ion-ion collisions on stability is found to be significant; collisionally young wind is much more unstable than collisionally old wind, with very different kinds of instabilities present in the two kinds of wind.

show abstract

Section: Introductionmentioning

confidence: 99%

Alfvénic velocity spikes and rotational flows in the near-Sun solar wind

Kasper¹,

Bale²,

Belcher³

et al. 2019

Nature

370

299

View full text Add to dashboard Cite

show abstract

“…With the establishment of satellite space missions, the near-Earth environment and the solar wind have provided unique opportunities to explore the physics of weakly collisional, magnetized plasmas (e.g., Bruno and Carbone, 2013;Chen, 2016;Verscharen et al, 2019). In particular, increasingly accurate in-situ measurements of plasma fluctuations and particle distribution functions from Cluster and MMS have uncovered an entire new world of kinetic processes occurring in plasma turbulence (e.g., Alexandrova et al, 2009Alexandrova et al, , 2012Alexandrova et al, , 2013Sahraoui et al, 2009Sahraoui et al, , 2010Chen et al, 2010Chen et al, , 2019Greco et al, 2016;Narita et al, 2016;Chasapis et al, 2017;Chen and Boldyrev, 2017;Huang et al, 2017;Roberts et al, 2017;Servidio et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Kinetic Plasma Turbulence: Recent Insights and Open Questions From 3D3V Simulations

Cerri

Grošelj

Franci

2019

Front. Astron. Space Sci.

View full text Add to dashboard Cite

Turbulence and kinetic processes in magnetized space plasmas have been extensively investigated over the past decades via in-situ spacecraft measurements, theoretical models and numerical simulations. In particular, multi-point high-resolution measurements from the Cluster and MMS space missions brought to light an entire new world of processes, taking place at the plasma kinetic scales, and exposed new challenges for their theoretical interpretation. A long-lasting debate concerns the nature of ion and electron scale fluctuations in solar-wind turbulence and their dissipation via collisionless plasma mechanisms. Alongside observations, numerical simulations have always played a central role in providing a test ground for existing theories and models. In this Perspective, we discuss the advances achieved with our 3D3V (reduced and fully) kinetic simulations, as well as the main questions left open (or raised) by these studies. To this end, we combine data from our recent kinetic simulations of both freely decaying and continuously driven fluctuations to assess the similarities and/or differences in the properties of plasma turbulence in the sub-ion range. Finally, we discuss possible future directions in the field and highlight the need to combine different types of numerical and observational approaches to improve the understanding of turbulent space plasmas.

show abstract

“…Several studies have investigated how the power spectrum of solar wind magnetic field fluctuations is in agreement with predictions made by turbulence theories (e.g., Coleman, 1968;Bavassano et al, 1982;Horbury and Balogh, 2001;Bale et al, 2005b;Tsurutani et al, 2018;Verscharen et al, 2019). Kolmogorov's spatially homogeneous hydrodynamic turbulence model gives f −5/3 (i.e., spectral index α = −1.67; Kolmogorov, 1941) and is based on the assumption that energy cascades from larger https://doi.org/10.5194/angeo-2020-17 Preprint.…”

Section: Spectral Indicesmentioning

confidence: 78%

“…Several studies have shown that fluctuations in the solar wind are typically strongly intermittent (e.g., Burlaga, 1991;Feynman and Ruzmaikin, 1994;Tu, 1994, 1997;Pagel and Balogh, 2001;Yordanova et al, 2009). Intermittency describes inhomogenity in the energy transfer between scales, and is manifested as a lack of self-similarity in fluctuation distributions between scales (see, e.g., reviews by Horbury et al, 2005;Sorriso-Valvo et al, 2005;Bruno, 2019;Verscharen et al, 2019).…”

Section: Intermittencymentioning

confidence: 99%

Magnetic field fluctuation properties of coronal mass ejection-driven sheath regions in the near-Earth solar wind

Kilpua¹,

Fontaine²,

Good³

et al. 2020

Preprint

View full text Add to dashboard Cite

Abstract. In this work, we investigate the magnetic field fluctuations in three coronal mass ejection (CME)-driven sheath regions at 1 AU with their speeds ranging from slow to fast. The data set we use consists primarily of high resolution (0.092 s) magnetic field measurements from the Wind spacecraft. We analyse magnetic field fluctuation amplitudes and fluctuation amplitudes normalised to the mean magnetic field, compressibility, and spectral properties of fluctuations. We also analyse intermittency using various approaches: we apply the partial variance of increments (PVI) method, investigate probability distribution functions of fluctuations, including their skewness and kurtosis, and perform a structure function analysis. Our analysis is conducted separately for three different subregions in the sheath and in the solar wind ahead of it, each 1 hr in duration. We find that, for all cases, the transition from the solar wind ahead to the sheath generates new fluctuations and the intermittency and compressibility increase, while the region closest to the ejecta leading edge resembled the solar wind ahead. The spectral indices exhibit large variability in different parts of the sheath, but are typically steeper than Kolmogorov's in the inertial range. The structure function analysis produced generally much better fit with the extended p-model (Kraichnan's form) than with the standard version, implying that turbulence is not fully developed in CME sheaths near Earth's orbit. The p-values obtained (p~0.8–0.9) also suggest relatively high intermittency. At the smallest timescales investigated, the spectral indices indicate relatively shallow slopes (between −2 and −2.5), suggesting that in CME-driven sheaths at 1 AU the energy cascade from larger to smaller scales could still be ongoing through the ion scale. Regarding many properties (e.g., spectral indices and compressibility) turbulent properties in sheaths, regardless their speed, resemble that of the slow wind, rather fast wind. They are also partly similar to properties reported in terrestrial magnetosheath, in particular regarding their intermittency, compressibility and absence of Kolmogorov's type turbulence. Our study also reveals that turbulent properties can vary considerably within the sheath. This was in particular the case for the fast sheath behind the strong and quasi-parallel shock, including a small, coherent structure embedded close to its midpoint. Our results support the view of the complex formation of the sheath and different physical mechanisms playing a role in generating fluctuations in them.

show abstract

The multi-scale nature of the solar wind

Cited by 302 publications

References 709 publications

Alfvénic velocity spikes and rotational flows in the near-Sun solar wind

Alfvénic velocity spikes and rotational flows in the near-Sun solar wind

Kinetic Plasma Turbulence: Recent Insights and Open Questions From 3D3V Simulations

Magnetic field fluctuation properties of coronal mass ejection-driven sheath regions in the near-Earth solar wind

Contact Info

Product

Resources

About