What causes the flux excess in the heliospheric magnetic field?

EJ Smith�- Journal of Geophysical Research: Space Physics, 2011 - Wiley Online Library
EJ Smith
Journal of Geophysical Research: Space Physics, 2011Wiley Online Library
Ulysses results indicate that the total magnetic flux inside the heliosphere, Φ, can be
obtained from the radial field component measured at a single spacecraft multiplied by the
square of the radial distance and averaged over a solar rotation,< r2BR>. However, that
result is contrary to a large increase in Φ with distance, called the flux excess, that has been
reported by Owens et al.(2008a) and attributed to variations in solar wind speed by
Lockwood et al.(2009a, 2009b). Ulysses data and a mathematical simulation are used to�…
Ulysses results indicate that the total magnetic flux inside the heliosphere, Φ, can be obtained from the radial field component measured at a single spacecraft multiplied by the square of the radial distance and averaged over a solar rotation, < r2BR >. However, that result is contrary to a large increase in Φ with distance, called the flux excess, that has been reported by Owens et al. (2008a) and attributed to variations in solar wind speed by Lockwood et al. (2009a, 2009b). Ulysses data and a mathematical simulation are used to show that the cause of the flux excess is the replacement of BR by the modulus, |BR|. The modulus rectifies some of the large amplitude magnetic field variations normally present in measurements of BR and increases the mean, < r2 |BR| > relative to < r2BR >. The variance of the magnetic fluctuations, σ, decreases less rapidly with distance than BR and that produces a progressively larger error in < r2 |BR| > resulting in the flux excess. The advisability of defining Φ in terms of |BR|, of using < r2 |BR| > beyond 1 AU and the applicability of the Lockwood et al. (2009b) correction to < r2 |BR| > are questioned.
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