A Review of Alfvénic Turbulence in High‐Speed Solar Wind Streams: Hints From Cometary Plasma Turbulence. Issue 4 (6th April 2018)

• Record Type: Journal Article
• Authors: Tsurutani, Bruce T.; Lakhina, Gurbax S.; Sen, Abhijit; Hellinger, Petr; Glassmeier, Karl‐Heinz; Mannucci, Anthony J.
• Is Part Of: Journal of geophysical research. Volume 123:Issue 4(2018)
• Page Start: 2458
• Page End: 2492
• Publication Date: 2018-04-06
• Subjects: interplanetary turbulence -- Alfvén waves -- magnetic decreases -- period doubling -- discontinuities -- wave phase‐steepening; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2017JA024203
• Languages: English
• ISSNs: 2169-9380

Abstract

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. Plain Language Summary: Interplanetary Alfvénic turbulence is studied from an observational microstructural viewpoint. We use cometary turbulence as a guide and for comparison to interplanetary turbulence. It is shown that single wave cycles reveal much of the ongoing physics. Alfvén waves phase‐steepen forming a high‐frequency end, leaving a low‐frequency end. This is a form of "wave breaking" and "period doubling" occurring at the same time. If Alfvén waves occur at all scale sizes, this can explain the Kolmogrov‐type spectra found in all studies. The interplanetary medium is also highly "compressive." This is caused by the magnetic decreases detected at the ends of the Alfvén waves. It is thought that this is a kinetic process associated with the dissipation of the Alfvén waves. The interplanetary Alfvén waves are often arc‐polarized spherical waves implying a local source of generation. Some theoretical mechanisms for local generation are cited. Finally, it is shown that the MDs can cause rapid cross‐field diffusion of energetic solar flare particles, perhaps explaining their broad distributions in solar longitude. Single cycle Alfvén waves impinging on the magnetosphere cause strong and continuous auroral activity. Key Points: Interplanetary turbulence in high‐speed streams is reviewed from a microstructual observational viewpoint for the first time Single wave characteristics can give information on the development of turbulence Single wave "period doubling" and "wave breaking" have been found