Magnetic flux density measured in fast and slow solar wind streams

G. Erdos, A. Balogh

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12 Citations (Scopus)


The radial component of the heliospheric magnetic field vector is used to estimate the open magnetic flux density of the Sun. This parameter has been calculated using observations from the Ulysses mission that covered heliolatitudes from 80°S to 80°N, from 1990 to 2009 and distances from 1 to 5.4AU, the Advanced Composition Explorer mission at 1AU from 1997 to 2010, the OMNI interplanetary database from 1971, and the Helios 1 and 2 missions that covered the distance range from 0.3 to 1AU. The flux density was found to be much affected by fluctuations in the magnetic field which make its calculated value dependent on heliospheric location, type of solar wind (fast or slow), and the level of solar activity. However, fluctuations are distributed symmetrically perpendicular to the average Parker direction. Therefore, distributions of the field vector in the two-dimensional plane defined by the radial and azimuthal directions in heliospheric coordinates provide a way to reduce the effects of the fluctuations on the measurement of the flux density. This leads to a better defined flux density parameter; the distributions modified by removing the effects of fluctuations then allow a clearer assessment of the dependence of the flux density on heliospheric location, solar wind type, and solar activity. This assessment indicates that the flux density normalized to 1AU is independent of location and solar wind type (fast or slow). However, there is a residual dependence on solar activity which can be studied using the modified flux density measurements.

Original languageEnglish
Article number130
JournalAstrophysical Journal
Issue number2
Publication statusPublished - Jul 10 2012



  • Sun: activity
  • magnetic fields
  • solar wind

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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