Quasilinear Theory of the Ion Cyclotron Instability and Its Application to the Cometary Plasma

  1. Alan Johnstone
  1. A. A. Galeev1,
  2. R. Z. Sagdeev3,
  3. V. D. Shapiro1,
  4. V. I. Shevchenko1 and
  5. K. Szego2

Published Online: 26 MAR 2013

DOI: 10.1029/GM061p0223

Cometary Plasma Processes

Cometary Plasma Processes

How to Cite

Galeev, A. A., Sagdeev, R. Z., Shapiro, V. D., Shevchenko, V. I. and Szego, K. (1991) Quasilinear Theory of the Ion Cyclotron Instability and Its Application to the Cometary Plasma, in Cometary Plasma Processes (ed A. Johnstone), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM061p0223

Author Information

  1. 1

    Space Research Institute, Profsoyuznaya 84/32, 117810 Moscow GSP-7, USSR

  2. 2

    Central Research Institute for Physics, Budapest, Hungary

  3. 3

    University of Maryland, Maryland 20742, USA

Publication History

  1. Published Online: 26 MAR 2013
  2. Published Print: 1 JAN 1991

ISBN Information

Print ISBN: 9780875900278

Online ISBN: 9781118663660



  • Comets;
  • Space plasmas;
  • Astrophysics


The quasilinear theory of Alfven turbulence in the mass-loaded solar wind is reviewed and compared with observations obtained in the upstream region of comet Halley's bow shock. The theory explains the formation of the shell distribution of the cometary ions from the initial ring distribution as the result of the pitch angle diffusion caused by Alfven waves. In situ measurements of wave intensity, frequency spectrum and polarisation of Alfven waves also agree well with the predictions of the ion cyclotron instability, driven by cometary ions. The turbulence in the vicinity of the comet Giacobini-Zinner seems to be somewhat different—while being more intense it is essentially more regular in its nature. The main reason for this difference is due to the fact that in the latter case, with smaller gas production rates, turbulence develops significantly closer to the comet.

The possibility of the excitation of oblique magnetosonic waves accompanied by density fluctuations is analysed. The mechanism for such excitation is wave refraction on the transverse inhomogeneities in the solar wind. It is shown that in the vicinity of the bow shock the intensity of magnetosonic waves grows rapidly.

The acceleration of the cometary ions in the mass-loaded solar wind by MHD turbulence (stochastic Fermi acceleration) is also analysed in the paper. It is shown that the softest part of the spectrum of the accelerated ions could be attributed to the acceleration by oblique magnetosonic waves while the main acceleration is due to the long wavelength firehose magnetic field perturbations. The ion energy spectra obtained by solving the energy diffusion equation are compared with observations.