TALK ABSTRACT:
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Large solar energetic particle (SEP) events are closely associated with coronal 
mass ejections (CMEs). It is thought that CME-driven shocks accelerate the SEPs.
One of the traditional supports for this connection is the correlation between 
SEP intensity and CME speed. However, these scatter plots often show a 3-4 
orders magnitude variation in SEP intensity for a given CME speed. We explore 
the possibility of CME interaction as a source of this scatter. We consider all 
the SEP events with intensity > 10 pfu in the GOES energy channel > 10 MeV. The 
SEP events can be divided into three groups: (i) those with preceding wide CMEs 
(P) within a day, (ii) those not preceded (NP) by wide CMEs within a day, and 
(iii) those with CMEs interacting with another one very close to the solar 
surface or with another CME (O). We find that group P has the highest median 
intensity and group NP has the lowest median intensity. Since most of the CME 
properties such as speed, width, mass, and kinetic energy are the same between P
and NP events, we conclude that the presence of preceding CMEs must have 
resulted in the high intensity of P events. This is further supported by the 
fact that most of the O events are also of high intensity (they interact with 
other CMEs close to the surface or with streamers). Considered separately, the 
scatter in the correlation plot reduces significantly. The preceding CMEs are, 
on the average, fast and wide, so they are capable of producing seed particles. 
The presence of preceding CMEs near the Sun implies that the shocks have to 
propagate through an ambient medium severely disturbed and distorted in density 
and magnetic field, rather than through a normal solar wind.

REFERENCES:

• CME Interaction and the Intensity of Solar Energetic Particle Events
• Intensity Variation of Large Solar Energetic Particle Events Associated with Coronal Mass Ejections
• Large solar energetic particle events of cycle 23: A global view
• Interacting Coronal Mass Ejections and Solar Energetic Particles
• Radio Signatures of Coronal Mass Ejection Interaction: Coronal Mass Ejection Cannibalism?