The multi-scale nature of the solar wind

Daniel Verscharen, Kristopher G. Klein, Bennett A. Maruca

Research output: Contribution to journalReview articlepeer-review

221 Scopus citations


The solar wind is a magnetized plasma and as such exhibits collective plasma behavior associated with its characteristic spatial and temporal scales. The characteristic length scales include the size of the heliosphere, the collisional mean free paths of all species, their inertial lengths, their gyration radii, and their Debye lengths. The characteristic timescales include the expansion time, the collision times, and the periods associated with gyration, waves, and oscillations. We review the past and present research into the multi-scale nature of the solar wind based on in-situ spacecraft measurements and plasma theory. We emphasize that couplings of processes across scales are important for the global dynamics and thermodynamics of the solar wind. We describe methods to measure in-situ properties of particles and fields. We then discuss the role of expansion effects, non-equilibrium distribution functions, collisions, waves, turbulence, and kinetic microinstabilities for the multi-scale plasma evolution.

Original languageEnglish (US)
Article number5
JournalLiving Reviews in Solar Physics
Issue number1
StatePublished - Dec 1 2019


  • Coulomb collisions
  • Kinetic instabilities
  • Plasma waves and turbulence
  • Solar wind
  • Spacecraft measurements

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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