Alfvén Radius: A Key Parameter for Astrophysical Magnetospheres

  • Elena S. BelenkayaEmail author
  • Maxim L. Khodachenko
  • Igor I. Alexeev
Part of the Astrophysics and Space Science Library book series (ASSL, volume 411)


The Alfvén radius is a distance where the magnetic energy density is equal to the kinetic energy density, or bulk velocity equals the Alfvén velocity. In this paper we discuss a role of Alfvén radius for different types of magnetospheres and magnetosphere-disk systems. Among the astrophysical disks considered here are the magnetic disks surrounding the outer planets in the Solar System (Jupiter and Saturn) and exoplanets, the heliospheric current sheet, accretion disks of neutron stars , pulsars, millisecond X-ray pulsars, white dwarfs and black holes, disks in the X-ray binaries , disks of young stars and active galactic nuclei (AGNs). We note that mainly in the magnetosphere-disk system, the inner edge of astrophysical disk (independently of its origin, direction of motion and material in it) in the presence of a strong magnetic field is located close to the Alfvén radius. For magnetized planets a concept of Alfvén radius is important as for the interaction with the solar/stellar wind, either for the inter-magnetospheric processes.


Black Hole Solar Wind Neutron Star Accretion Disk Stellar Wind 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



The authors acknowledge the support by the International Space Science Institute (ISSI) in Bern, Switzerland and the ISSI team Characterizing stellar- and exoplanetary environments. This work was carried out at the Institute of Nuclear Physics, Moscow State University and was supported by the RFBR Grants 11-05-00894-a, 12-05-00219-a, and 12-02-92600-KO-a, by the EU FP7 projects EUROPLANET/JRA3 and IMPEX (no. 262863). The authors acknowledge also the support by the Austrian Research Foundation FWF NFN project S116 ’Pathways to Habitability: From Disks to Active Stars, Planets and Life’, and the related FWF NFN subproject, S116 606-N16 ’Magnetospheric Electrodynamics of Exoplanets’. This work was also supported by the FWF project P21197-N16.


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Copyright information

© Springer International Publishing Switzerland 2015

Authors and Affiliations

  • Elena S. Belenkaya
    • 1
    Email author
  • Maxim L. Khodachenko
    • 1
    • 2
  • Igor I. Alexeev
    • 1
  1. 1.Skobeltsyn Institute of Nuclear Physics (MSU SINP)Lomonosov Moscow State UniversityMoscowRussian Federation
  2. 2.Austrian Academy of SciencesSpace Research InstituteGrazAustria

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