HR: 17:00h
AN: NG34A-05    [Abstracts]
TI: Generalized Reynolds numbers and points of contact between intermittent turbulence and Self Organized Criticality
AU: Rowlands, G
EM: G.Rowlands@warwick.ac.uk
AF: Centre for Fusion, Space and Astrophysics, Physics Dept., Univ. of Warwick, Coventry, CV4 7AL, United Kingdom
AU: * Chapman, S C
EM: S.C.Chapman@warwick.ac.uk
AF: Centre for Fusion, Space and Astrophysics, Physics Dept., Univ. of Warwick, Coventry, CV4 7AL, United Kingdom
AU: Watkins, N W
EM: NWW@bas.ac.uk
AF: Physical Sciences Division, British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB1 1UJ, United Kingdom
AB: Self Organised Criticality (SOC) has received considerable attention in the context of bursty, intermittent plasma transport and energy release in the earth's magnetotail. This phenomenology can also be characterized in the context of intermittent turbulence. Here we elucidate a key similarity, and difference, between turbulence, and SOC. In fluid turbulence a single control parameter, the Reynolds number R_E, which is a function of macroscopic system variables is sufficient to quantify the transition from ordered (laminar) to disordered (turbulent) flow. We suggest that a wider class of systems has this property including Self Organized Criticality (SOC). These systems can all be driven into a state with defining characteristics: they have many degrees of freedom (d.o.f.); are driven, dissipating and out of equilibrium; are on average in a steady state; and show scaling over a large dynamic range. The Reynolds number expresses the number of d.o.f., or energy carrying modes in the system. For avalanche models exhibiting SOC, d.o.f. refer to avalanche sizes and the Reynolds number R_A that we identify is simply the well known ratio of the driving rate to system dissipation rate. The SOC slowly driven interaction dominated limit is reached by taking R_A to zero; we show this maximizes the number of d.o.f. in the opposite sense to fluid turbulence. This result clarifies the much debated relationship between turbulence and SOC. A corollary is that for a sufficiently large system, SOC - like behaviour can occur at finite driving rates, important if SOC is a mechanism operating in real physical systems.
DE: 2740 Magnetospheric configuration and dynamics
DE: 4425 Critical phenomena
DE: 4430 Complex systems
DE: 4480 Self-organized criticality
DE: 4490 Turbulence (3379, 4568, 7863)
SC: Nonlinear Geophysics [NG]
MN: 2007 Fall Meeting