Mechanism of proton anisotropic velocity distribution in the solar wind

Xianzhi Ao, Ji Shen, Chuanyi Tu

Research output: Contribution to journalArticlepeer-review


Although it has been long that spacecraft observed the anisotropy of velocity protons in the solar wind, there is still not a reasonable explanation. In this paper we try to give an explanation from the diffusion plateau of proton cyclotron resonance predicted by the quasi-linear theory for the resonance between the protons and the parallel propagating waves. We consider the effect of dispersion relation on diffusion plateau and notice that the diffusion plateau we have got by using cold plasma dispersion relation accords with the density contours in the velocity phase space detected at 0.3 AU in fast solar wind. For explaining proton distributions obtained in the fast solar wind from 0.7 AU to 1 AU hot plasma dispersion relation should be considered. We also give a theoretical relation of proton thermal anisotropy A and plasma parameter β.

Original languageEnglish (US)
Number of pages1
JournalScience in China, Series G: Physics Astronomy
Issue number1
StatePublished - Dec 1 2003
Externally publishedYes


  • Cyclotron resonance
  • Diffusion plateau
  • Quasi-linear theory
  • Solar wind

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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