How Soft Gamma Repeaters May Make Fast Radio Bursts

There are several phenomenological similarities between Soft Gamma Repeaters and Fast Radio Bursts, including duty factors, time scales and probable repetition. The sudden release of magnetic energy in a neutron star magnetosphere, as in popular models of SGR, can meet the energy requirements of FRB but requires both the presence of magnetospheric plasma in order that dissipation occur in a transparent region and a mechanism for releasing much of that energy quickly. FRB sources and SGR are distinguished by long-lived (up to thousands of years) current-carrying coronal arches remaining from formation of the young neutron star and their decay ends the phase of SGR/AXP/FRB activity even though “magnetar” fields may persist. Runaway increase in resistance when the current density exceeds a threshold releases magnetostatic energy in a sudden burst and produces high brightness GHz emission of FRB by a coherent process; SGR are produced when released energy thermalizes as an equilibrium pair plasma. Failures of some alternative FRB models and the non-detection of SGR~1806-20 at radio frequencies are discussed in appendices.