Core, Halo and Strahl Electrons in the Solar Wind

  • Viviane Pierrard
  • Milan Maksimovic
  • Joseph Lemaire
Conference paper


Electron velocity distribution functions (VDF) observed in the low speed solar wind flow are generally characterized by ‘core’ and ‘halo’ electrons. In the high speed solar wind, a third population of ‘strahl’ electrons is generally observed. New collisional models based on the solution of the Fokker-Planck equation can be used to determine the importance of the different electron populations as a function of the radial distance. Typical electron velocity distribution functions observed at 1 AU from the Sun are used as boundary conditions for the high speed solar wind and for the low speed solar wind. Taking into account the effects of external forces and Coulomb collisions with a background plasma, suprathermal tails are found to be present in the electron VDF at low altitudes in the corona when they exist at large radial distances.


Solar Wind Speed Solar Wind Velocity Distribution Function Coulomb Collision Fast Solar Wind 
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Copyright information

© Springer Science+Business Media New York 2001

Authors and Affiliations

  • Viviane Pierrard
    • 1
  • Milan Maksimovic
    • 2
  • Joseph Lemaire
    • 1
  1. 1.Institut d’Aéronomie Spatiale de BelgiqueBrusselsBelgium
  2. 2.DESPAObservatoire de Paris-MeudonFrance

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