Magnetic explosions: role of the inductive electric field

Inclusion of the inductive electric field, ${\mathbf{E}}_{\mathrm{i}\mathrm{n}\mathrm{d}}$ due to the temporally changing $\mathbf{B}$, in magnetic explosions is discussed, with emphasis on solar flares. Several roles played by ${\mathbf{E}}_{\mathrm{i}\mathrm{n}\mathrm{d}}$ are identified: on a global scale, ${\mathbf{E}}_{\mathrm{i}\mathrm{n}\mathrm{d}}$ produces the EMF that drives the explosion; the associated ${\mathbf{E}}_{\mathrm{i}\mathrm{n}\mathrm{d}}\times \mathbf{B}$ drift is identified with the inflow of magnetic field lines into a reconnection region; the polarization current, associated with $\partial{\bf E}_{\rm ind}/\partial t$,impliesa${\bf J}\times{\bf B}$ force that accelerates this inflow; and the component of ${\mathbf{E}}_{\mathrm{i}\mathrm{n}\mathrm{d}}$ parallel to $\mathbf{B}$ accelerates the energetic electrons that cause hard X-ray emission and type III radio bursts. Some simple models that describe these effects are presented. A resolution of the long-standing “number problem” in solar flares is suggested.