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[54.01] The delta spot and active region cutoff energies

I. Sammis, H. Zirin (Solar Astronomy, California Institute of Technology)

It has been demonstrated observationally (Kucera et al. 1997) that active regions have a cutoff flare energy (E_c) beyond which their flare production is sharply restricted. This cutoff energy appears to vary with active region area. Flare models have been created which predict this (Lu et al 1993., Litvinenko 1996 for example); these models predict a form E_c(L), where L is some measure of the extent of the active region.

Using USAF and Mt. Wilson active region observations for active regions in the years 1989-1997, we see that great flares tend to be produced by complex delta spots (delta spots with a Mt. Wilson classification of \beta \gamma). This argues for a more complex functional form E_c(L,\ldots ), where the additional parameters would describe in some way the magnetic configuration.

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