Subphotospheric current systems and flares

Subphotospheric current systems inferred from recent vector magnetograph observations (e.g. Gary et al., 1987) imply the existence of electric currents penetrating the photosphere and thus flowing deep in the solar convection zone. These currents presumably originate in an internal dynamo that supplies the observed photospheric magnetic fields through the buoyant motions of the initially deeply-buried flux tubes. The coronal fields resulting from this process therefore must carry slowly-varying currents driven by emf's remote from the surface. These currents may then drive solar-flare energy release. This paper discusses the consequences of such a deep origin of the coronal parallel currents. Simple estimates for a large active region suggest a mean current-closure depth 10,000 km, with a subphotospheric inductance 100 H and a subphotospheric stored energy 10³³ ergs.