The researchers led by Professor Sandra Chapman at the University of Warwick, used "finite size scaling" to look at the probability of fluctuations or jumps in magnetic energy density in the solar wind, using data from the NASA-WIND spacecraft. They found that the solar wind fluctuations had a much higher probability of extreme events than for more familiar random processes (which follow a Gaussian or bell shaped curve). In fact statistically, the solar wind fluctuations are similar to those found previously for fluctuations in stock market indices. Large fluctuations in the solar wind affect our local 'space weather'. Predicting these is as challenging as predicting large changes in stock prices. As this work suggests that the underlying mathematics is similar we can apply knowledge from one area to understand the other.
The researchers also found that the magnetic energy density fluctuations were self-similar (in that the pattern of variations looked very similar at all time scales up to a period of 20 hours or so – in the same way that a fractal image tends to show very similar properties or patterns when you look at it on different scales). The team members are using their new analysis to modify current turbulence theories to produce more useful mathematical models of the occurrence of extreme events in the solar wind. The research team's first paper is entitled "B. Hnat, S.C. Chapman, G. Rowlands, N.W. Watkins and W. M. Farrell, Finite size in the solar wind magnetic field energy density as seen by WIND, Geophys. Res. Lett., 29, 86-1, (2002). The authors are from the University of Warwick, the British Antarctic Survey (BAS) and NASA Goddard Space Flight Center.
Note for Editors: The University of Warwick analysis was supported at the Warwick end by the Particle Physics and Astronomy Research Council, and at BAS by the Natural Environment Research Council.
For further information contact:
Professor Sandra Chapman, Space and Astrophysics Group,
University of Warwick email: sandrac@astro.warwick.ac.uk
Tel: 02476 523390 http://www.astro.warwick.ac.uk
mobile 07740291984
Geophysical Research Letters