APPEARANCE AND NONAPPEARANCE OF SELF-ORGANIZED CRITICALITY IN SANDPILES

Self-organized criticality (SOC) often features in sandpile-type model ing of complex systems such as magnetic fusion plasmas, but its observ ed role in real sandpiles is equivocal. Here, a probabilistic model di splaying some of the observed phenomenology of real sandpiles is propo sed. It generates avalanches involving particle loss that, like most e xperiments, do not exhibit SOC, but its internal energy avalanches res emble recent experiments by showing SOC. This suggests that the absenc e of SOC in the flow of matter from such systems can be consistent wit h internal dynamics governed by SOC.