Strength of Coronal Mass Ejection-Driven Shocks Near the Sun and Their Importance in Predicting Solar Energetic Particle Events

Coronal shocks are an important structure but without direct observations in solar and space physics. The strength of shocks plays a key role in shock-related phenomena, such as radio bursts, SEP generation and so on. This paper will present an improved method of calculating ă and shock strength near the Sun. In the method, observations as many as possible rather than one-dimensional global models are used. Two events, a relatively slow CME on 2001 September 15 and a very fast CME on 2000 June 15, are selected to illustrate the calculation process. The calculation results suggest that the slow CME drove a strong shock with Mach number of 3.43~4.18 while the fast CME drove a relatively weak shock with Mach number of 1.90~3.21. This is consistent with the radio observations that a stronger and longer decameter-hectometric (DH) type II radio burst is found during the first event and a short DH type II radio burst during the second event. Particularly, the calculation results explain the observational fact that the slow CME produced a major solar energetic particle (SEP) event while the fast CME did not. Through the comparison between the two events, the importance of shock strength in predicting SEP events is addressed.