Heliospheric Evolution of Magnetic Clouds

Academic Article


  • Interplanetary evolution of eleven magnetic clouds (MCs) recorded by at least two radially aligned spacecraft is studied. The in situ magnetic field measurements are fitted to a cylindrically symmetric Gold-Hoyle force-free uniform-twist flux-rope configuration. The analysis reveals that in a statistical sense the expansion of studied MCs is compatible with self-similar behavior. However, individual events expose a large scatter of expansion rates, ranging from very weak to very strong expansion. Individually, only four events show an expansion rate compatible with the isotropic self-similar expansion. The results indicate that the expansion has to be much stronger when MCs are still close to the Sun than in the studied 0.47 - 4.8 AU distance range. The evolution of the magnetic field strength shows a large deviation from the behavior expected for the case of an isotropic self-similar expansion. In the statistical sense, as well as in most of the individual events, the inferred magnetic field decreases much slower than expected. Only three events show a behavior compatible with a self-similar expansion. There is also a discrepancy between the magnetic field decrease and the increase of the MC size, indicating that magnetic reconnection and geometrical deformations play a significant role in the MC evolution. About half of the events show a decay of the electric current as expected for the self-similar expansion. Statistically, the inferred axial magnetic flux is broadly consistent with it remaining constant. However, events characterized by large magnetic flux show a clear tendency of decreasing flux.
  • Authors

  • Vrsnak, B
  • Amerstorfer, T
  • Dumbovic, M
  • Leitner, M
  • Veronig, AM
  • Temmer, M
  • Moestl, C
  • Amerstorfer, UV
  • Farrugia, Charles
  • Galvin, AB
  • Status

    Publication Date

  • June 1, 2019
  • Has Subject Area


  • Sun: coronal mass ejections (CMEs)
  • Sun: heliosphere
  • magnetic reconnection
  • magnetohydrodynamics (MHD)
  • methods: observational
  • solar wind
  • Digital Object Identifier (doi)

    Start Page

  • 77
  • End Page

  • 77
  • Volume

  • 877
  • Issue

  • 2