A Solar Cycle Dependence of Nonlinearity in Magnetospheric Activity
Abstract
The nonlinear dependencies inherent to the historical Kp data stream (1932-2003) are examined using mutual information and cumulant based cost as discriminating statistics. The discriminating statistics are compared with surrogate data streams that are constructed using the corrected amplitude adjustment Fourier transform (CAAFT) method and capture the linear properties of the original Kp data. Differences are regularly seen in the discriminating statistics a few years prior to solar minima, while no differences are apparent at the time of solar maximum. These results suggest that the dynamics of the magnetosphere tend to be more linear at solar maximum than at solar minimum. The strong nonlinear dependencies tend to peak on a timescale around 40-50 hours and are statistically significant up to one week. Because the solar wind driver variables, VBs and dynamical pressure exhibit a much shorter decorrelation time for nonlinearities the results seem to indicate that the nonlinearity is related to internal magnetospheric dynamics. Because the timescales for the nonlinearity seem to be on the same order as that for storm/ring current relaxation, we suggest that the nonlinearity is likely associated with those processes.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2004
- Bibcode:
- 2004AGUFMSM43A1134J
- Keywords:
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- 7839 Nonlinear phenomena;
- 2722 Forecasting;
- 2784 Solar wind/magnetosphere interactions;
- 3220 Nonlinear dynamics