Prediction of the 1‐AU arrival times of CME‐associated interplanetary shocks: Evaluation of an empirical interplanetary shock propagation model

The traveltimes of interplanetary (IP) shocks at 1 AU associated with coronal mass ejections (CMEs) can be predicted by the empirical shock arrival (ESA) model of Gopalswamy et al. [2004] based on a constant IP acceleration. We evaluate the ESA model using 91 IP shocks identified from sudden commencement (SC)/sudden impulse (SI) on the Earth and by examining the solar wind data from the ACE and WIND satellites during the period of 1997 to 2002. Out of 91 CME‐IP shock pairs, 55 events (∼60%) were predicted within ±12 hours from the ESA model. The ESA model predicted ∼59% (43 out of 73) of the events during solar maximum (1999–2002) and ∼67% (12 out of 18) of the events during solar minimum (1997–1998) within ±12 hours from the predicted curve. Comparing the predicted ( T mod ) and observed ( T obs ) shock arrival times during solar maximum, we find that the deviations (Δ T = T obs − T mod ) of shock arrival times from the ESA model strongly correlate with the CME initial speeds ( V CME ) (linear correlation, r = 0.77). Such a strong correlation indicates that the constant IP acceleration in the ESA model is not reasonably well applied for all V CME . From the linear regression analysis, we obtain a linear fit to the relationship ( r = −0.62) between IP shock traveltime T (in hours) and V CME (in kilometer per second) during the solar maximum, which can be expressed as T = 76.86 − 0.02 V CME . In addition, we find that the IP shocks associated with the fast CMEs corresponding to strong SC/SI events have short traveltimes compared with other fast CMEs and that there is a negative correlation between the SC/SI strength and the IP shock traveltime. We suggest that this negative correlation is due to not only the V CME but also the CME mass/density and discuss the influence of the mass/density of CME on the arrival time of IP shock at 1 AU.