HR: 1340h
AN: SM43A-1215    [Abstracts]
TI: Nonlinearity in Kp and its implication to Kp forecasting
AU: Meng, C
EM: ching.meng@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Lab, 11100 Johns Hopkins Road, Laurel, MD 20723 United States
AU: * Wing, S
EM: simon.wing@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Lab, 11100 Johns Hopkins Road, Laurel, MD 20723 United States
AU: Johnson, J R
EM: jrj@pppl.gov
AF: Princeton University Princeton Plasma Physics Lab, Princeton, Princeton, NJ 08543 United States
AB: Kp index has been used as a proxy for global geomagnetic activity level. Cumulant based analysis of Kp from 1932 to 2003 reveals linear and nonlinear correlations of Kp(t) and Kp(t - tau). The linear correlation peaks at tau = 0 hour and drops off rapidly after a few hours, suggesting that the persistence in Kp is in the order of a few hours. While the linear response is roughly the same for solar minimum and solar maximum, there is sharp difference in the nonlinear response. Near solar maximum, the nonlinear correlation follows closely the behavior of the linear correlation. In contrast, near solar min, the nonlinear correlation has a peak at tau = 0 hour and a secondary peak around tau = 40 hours. In fact, the nonlinear response appears to roughly anti-correlate with the sun spot number in every solar cycle since 1932. Several solar wind driven Kp forecast models were evaluated with data that spans over two solar cycles, 1975 - 2001. The evaluations show that the models predict Kp more accurately during solar maximum than solar minimum. All together, the results suggest that geospace is more dominated by internal dynamics during solar minimum than solar maximum, when it is more directly driven by external inputs, namely solar wind and IMF.
DE: 2722 Forecasting (7924, 7964)
DE: 2740 Magnetospheric configuration and dynamics
DE: 2784 Solar wind/magnetosphere interactions
DE: 2788 Magnetic storms and substorms (7954)
DE: 7924 Forecasting (2722)
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005