We have developed a new procedure for combining lists of substorm onset
times from multiple sources. We apply this procedure to observational
data and to magnetohydrodynamic (MHD) model output from 1-31 January,
2005. We show that this procedure is capable of rejecting false positive
identifications and filling data gaps that appear in individual lists.
The resulting combined onset lists produce a waiting time distribution
that is comparable to previously published results, and superposed epoch
analyses of the solar wind driving conditions and magnetospheric
response during the resulting onset times are also comparable to
previous results. Comparison of the substorm onset list from the MHD
model to that obtained from observational data reveals that the MHD
model reproduces many of the characteristic features of the observed
substorms, in terms of solar wind driving, magnetospheric response, and
waiting time distribution. Heidke skill scores show that the MHD model
has statistically significant skill in predicting substorm onset times.