| Abstract: | We evaluated the force-free factor α for 18 well-observed proton flare regions during 1967–1972 according to the degree of twist in their neutral line. We found that, on the day of the flare, α ≥ 0.34 for flares of Class 1 or greater and ≥ 0.50 for Class 2 or greater and that α always increased over the one or two days before the flare. We therefore suggest that α can be used in forecasting proton events. We also outline a squeezing force-free field model of large flares which can better explain certain observed facts. |
