Self-Organized Criticality and Sunspot Groups

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Session 86 -- Solar Active Regions
Display presentation, Wednesday, 11, 1995, 9:20am - 6:30pm

[86.03] Self-Organized Criticality and Sunspot Groups

John S. Neff (Department of Physics and Astronomy, University of Iowa )

A self-organized critical state can occur when a physical system continually driven toward instability tends to relax toward a stable state. As a result fluctuations can occur about a stable state that are characterized by $1/f$ noise in power output and power law distributions in size and energy output.

Temporal variations in the number and area of sunspot groups exhibit $1/f$ noise and the distributions of sunspot group area and lifetime are power laws. These are hallmarks of a self-organized critical process. In addition, the distribution of solar flare size is a power law that extends over five orders of magnitude. Lu and Hamilton have published a model for solar flares that is based on the proposition that the coronal magnetic field is in a self-organized critical state and that flares are an avalanche of many small reconnection events.

A logical extension of the Lu and Hamilton flare model can be used to simulate the temporal variations in the morphology of the magnetic field structure of a bipolar spot group. Simulations from such a model will be presented and compared with observations.

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