HR: 0830h
AN: SM41A-05    [Abstracts]
TI: Nonlinearity in Magnetospheric Activity and the Solar Cycle
AU: * Johnson, J R
EM: jrj@pppl.gov
AF: Princeton University, Plasma Physics Laboratory, PO Box 451, Princeton, NJ 08525 United States
AU: Wing, S
EM: simon.wing@jhuapl.edu
AF: The Johns Hopkins University/Applied Physics Laboratory, Johns Hopkins Road, Laurel, MD 20723 United States
AB: Nonlinearities inherent to the historical data stream of the K_p index from 1932 to present are examined using mutual information and cumulant based cost as discriminating statistics. The discriminating statistics are compared with surrogate data streams that share the same linear properties as the historical data set. 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. The result suggests 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, VB_s 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. Moreover, the timescales for the nonlinearity seem to be on the same order as that for storm/ring current relaxation. We suggest that the strong solar wind driving that occurs around solar maximum dominates the magnetospheric dynamics suppressing the internal magnetospheric nonlinearity. On the other hand, in the descending phase of the solar cycle just prior to solar minimum, when magnetospheric activity is weaker, the dynamics exhibit a significant nonlinear internal magnetospheric response that may be related to increased solar wind speed.
UR: http://w3.pppl.gov/~jrj/cumulant.html
DE: 2722 Forecasting
DE: 2784 Solar wind/magnetosphere interactions
DE: 3220 Nonlinear dynamics
SC: SPA-Magnetospheric Physics [SM]
MN: 2005 Joint Assembly