TOPOLOGY AND CURRENT RIBBONS - A MODEL FOR CURRENT, RECONNECTION AND FLARING IN A COMPLEX, EVOLVING CORONA

Magnetic field enters the corona from the interior of the Sun through isolated magnetic features on the solar surface. These features corres pond to the tops of submerged magnetic flux tubes, and coronal field l ines often connect one flux tube to another, defining a pattern of int er-linkage. Using a model field, in which flux tubes are represented a s point magnetic charges, it is possible to quantify this inter-linkag e. If the coronal field were current-free then motions of the magnetic features would change the inter-linkage through implicit (vacuum) mag netic reconnection. Without reconnection the conductive corona develop s currents to avoid changing the flux linkage. This current forms sing ular layers (ribbons) flowing along topologically significant field li nes called separators. Current ribbons store magnetic energy as intern al stress in the field: the amount of energy stored is a function of t he flux tube displacement. To explore this process we develop a model called the minimum-current corona (MCC) which approximates the current arising on a separator in response to displacement of photospheric fl ux. This permits a model of the quasi-static evolution of the corona a bove a complex active region. We also introduce flaring to rapidly cha nge the flux inter-linkage between magnetic features when the internal stress on a separator becomes too large. This eliminates the separato r current and releases the energy stored by it. Implementation of the MCC in two examples reveals repeated flaring during the evolution of s imple active regions, releasing anywhere from 10(27)-10(29) ergs, at i ntervals of hours. Combining the energy and frequency gives a general expression for heat deposition due to flaring (i.e., reconnection).