A Review of Alfvénic Turbulence in High‐Speed Solar Wind Streams: Hints From Cometary Plasma Turbulence

Abstract

Solar wind turbulence within high‐speed streams is reviewed from the point of view of embedded single nonlinear Alfvén wave cycles, discontinuities, magnetic decreases (MDs), and shocks. For comparison and guidance, cometary plasma turbulence is also briefly reviewed. It is demonstrated that cometary nonlinear magnetosonic waves phase‐steepen, with a right‐hand circular polarized foreshortened front and an elongated, compressive trailing edge. The former part is a form of “wave breaking” and the latter that of “period doubling.” Interplanetary nonlinear Alfvén waves, which are arc polarized, have a ~180° foreshortened front and with an elongated trailing edge. Alfvén waves have polarizations different from those of cometary magnetosonic waves, indicating that helicity is a durable feature of plasma turbulence. Interplanetary Alfvén waves are noted to be spherical waves, suggesting the possibility of additional local generation. They kinetically dissipate, forming MDs, indicating that the solar wind is partially “compressive” and static. The ~2 MeV protons can nonresonantly interact with MDs leading to rapid cross‐field (~5.5% Bohm) diffusion. The possibility of local (~1 AU) generation of Alfvén waves may make it difficult to forecast High‐Intensity, Long‐Duration AE Activity and relativistic magnetospheric electrons with great accuracy. The future Solar Orbiter and Solar Probe Plus missions should be able to not only test these ideas but to also extend our knowledge of plasma turbulence evolution.

Solar wind and kinetic heliophysics

“…sphere (Tu and Marsch, 1995), in particular in fast solar wind streams originating from coronal holes. A recent detailed review of the properties of Alfvénic turbulence in high-speed solar wind streams (with hints from cometary plasma turbulence) was published by Tsurutani et al (2018).…”

“…also showed that the compressible fluctuations are mostly slow-mode waves. A modern comprehensive general review of MHD turbulence, including a section on intermittency not dealt with here, was provided byBruno and Carbone (2013).Given all these observations, a two-component turbulence model(Tu and Marsch, 1993) with Alfvén waves parallel to the mean field and two-dimensional perpendicular turbulence superposed on magnetic flux tubes was suggested and diswww.ann-geophys.net/36/1607/2018/ Ann. Geophys., 36, 1607-1630, 2018…”

Waves in Kinetic‐Scale Magnetic Dips: MMS Observations in the Magnetosheath

“…The KSMD structures have similar observational characteristics to the magnetic mirror mode (MM; Tsurutani et al, 1982;Yao, Shi, Liu, et al, 2018), magnetic hole (MH), and interplanetary magnetic decreases (MD; Shi et al, 2009;Tsurutani et al, 1994Tsurutani et al, , 1999Tsurutani, Dasgupta, et al, 2002;Tsurutani et al, 2009;Xiao et al, 2010Xiao et al, , 2014 reported in previous studies; however, their formation processes and relevant physics are distinct. The classifications, generation mechanisms, and related studies (e.g., proton cyclotron and Langmuir waves inside the MD) for the MM, MH, and MD are well discussed by Tsurutani et al (2011) and related works (Lin et al, 1996;Tsurutani, Dasgupta, et al, 2002;Tsurutani et al, 2005Tsurutani et al, , 2018.…”

Highly Alfvénic slow solar wind at 0.3 au during a solar minimum: Helios insights for Parker Solar Probe and Solar Orbiter

“…On the one hand, on these large scales the magnetic field spectrum of the fast wind is characterised by a 1/ f scaling. The origin of this scaling is still under debate (Matthaeus & Goldstein 1986;Velli et al 1989;Dmitruk & Matthaeus 2007;Verdini et al 2012;Chandran 2018;Matteini et al 2018;Tsurutani et al 2018), but it probably corresponds to the large-scale energy in the eddies able to feed the turbulent cascade. During the solar wind expansion, the break between the large scales and the inertial range, which corresponds to the correlation length, moves to even larger scales (Matthaeus & Goldstein 1982;Bruno & Dobrowolny 1986;Horbury et al 1996), thus corresponding to an increase in the correlation length.…”