Combined first and second order Fermi acceleration at comets

T. I. Gombosi, K. Lorencz, J. R. Jokipii

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Our two-dimensional, time-dependent model calculations indicate that an interplay between velocity and spatial diffusion may be responsible for the acceleration of implanted heavy ions in the cometary preshock region. Velocity diffusion (second order Fermi acceleration) accelerates the pickup ions to moderate energies thus creating a seed population for the more efficient diffusive-compressive shock acceleration. Solar wind convection limits the time available for diffusive-compressive acceleration, therefore the resulting energy spectrum above 100 keV is a power law with a spectral index of 5 - 6, a value which is in reasonably good agreement with observations.

Original languageEnglish (US)
Pages (from-to)337-341
Number of pages5
JournalAdvances in Space Research
Issue number3
StatePublished - 1989

ASJC Scopus subject areas

  • Aerospace Engineering
  • Astronomy and Astrophysics
  • Geophysics
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences(all)


Dive into the research topics of 'Combined first and second order Fermi acceleration at comets'. Together they form a unique fingerprint.

Cite this