Joint Astrophysics Colloquium

Observational inferences of the power-law frequency distribution of energy release by solar flares, and in particular its logarithmic slope (α) depend critically on the geometrical relationship assumed to relate the observed emitting area (A) to the underlying emitting volume (V). Recent results on the fractal nature of avalanches in self-organized critical models for solar flares indicate that this relationship is a power law log(V)~γ log(A), with γ=1.4. After reviewing some basic flare physics and the potential role flares might play in coronal heating, I will give an overview of avalanche models for solar flares. I will then demonstrate that when proper account is made for the complex geometry of the flaring volume, hitherto discrepant observational inferences of α are brought in much closer agreement. The resulting values of α lie tantalizingly close, but still below the critical value α=2.0 beyond which Parker's conjecture of coronal heating by nanoflares is tenable.

Thursday, November 21st 2002, 12:00
Ernest Rutherford Physics Building, room 305