The Emission and Propagation of ~40 keV Solar Flare Electrons. II: The Electron Emission Structure of Large Active Regions

An early cartoon from the heyday of work on "Solar Cosmic Rays," or SEPs as they're more generically called now. It was crafted by one of the Archivist's oldest friends and colleagues not long after his PhD work. This paper was one of the pioneering works on the emission of electrons at mildly relativistic energies, and the author wanted to describe an extended source of such particles in order to explain the extended bundle of solar-wind field lines on which one could simultaneously see fast electrons. Type III bursts are part of the picture, of course, but note that there is no hint yet of magnetic reconnection in this cartoon. Open fields, yes, but only vaguely associated with the flare loops; also, nowadays, we don't identify a low-coronal diffusion region as such. A more modern cartoon (with color) does not shed much additional light on this still-perplexing problem of particle access.