@article{Matteini:2020,
author = {Matteini, L and Franci, L and Alexandrova, O and Lacombe, C and Landi, S and Hellinger, P and Papini, E and Verdini, A},
journal = {Frontiers in Astronomy and Space Sciences},
title = {Magnetic field turbulence in the solar wind at sub-ion scales: in situ  observations and numerical simulations},
url = {http://arxiv.org/abs/2008.13219v1},
year = {2020}
}

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TY  - JOUR
AB  - We investigate the transition of the solar wind turbulent cascade from MHD tosub-ion range by means of a detail comparison between in situ observations andhybrid numerical simulations. In particular we focus on the properties of themagnetic field and its component anisotropy in Cluster measurements and hybrid2D simulations. First, we address the angular distribution of wave-vectors inthe kinetic range between ion and electron scales by studying the varianceanisotropy of the magnetic field components. When taking into account thesingle-direction sampling performed by spacecraft in the solar wind, the mainproperties of the fluctuations observed in situ are also recovered in ournumerical description. This result confirms that solar wind turbulence in thesub-ion range is characterized by a quasi-2D gyrotropic distribution ofk-vectors around the mean field. We then consider the magnetic compressibilityassociated with the turbulent cascade and its evolution from large-MHD tosub-ion scales. The ratio of field-aligned to perpendicular fluctuations,typically low in the MHD inertial range, increases significantly when crossingion scales and its value in the sub-ion range is a function of the total plasmabeta only, as expected from theoretical predictions, with higher magneticcompressibility for higher beta. Moreover, we observe that this increase has agradual trend from low to high beta values in the in situ data; this behaviouris well captured by the numerical simulations. The level of magnetic fieldcompressibility that is observed in situ and in the simulations is in fairlygood agreement with theoretical predictions, especially at high beta,suggesting that in the kinetic range explored the turbulence is supported bylow-frequency and highly-oblique fluctuations in pressure balance, like kineticAlfv\'en waves or other slowly evolving coherent structures.
AU  - Matteini,L
AU  - Franci,L
AU  - Alexandrova,O
AU  - Lacombe,C
AU  - Landi,S
AU  - Hellinger,P
AU  - Papini,E
AU  - Verdini,A
PY  - 2020///
SN  - 2296-987X
TI  - Magnetic field turbulence in the solar wind at sub-ion scales: in situ  observations and numerical simulations
T2  - Frontiers in Astronomy and Space Sciences
UR  - http://arxiv.org/abs/2008.13219v1
ER  - 

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