A unified view of recently observed multiple coupling among cloud-to-ground, cloud-to-cloud, and cloud-to-ionosphere discharges, based on joint effects of electric reconnection and critical velocity

Summary form only given. This paper attempts to explain recently observed multiple coupling among cloud-to-ground, cloud-to-cloud, and cloud-to-ionosphere discharges on the basis of joint effects of electric reconnection and critical velocity. These observations indicate that the cloud shape and charge distribution is thought to be inclined and extended rather horizontally with a sequence of electrically cusped charge distribution or horizontal double layers in contrast to the usual charge structure in the form of a vertical double layer. Such a horizontal extent of cloud clusters is possibly due to stratospheric jet streams above the topside clouds in a way similar to the cloud and charge distribution in a coastal region of the Sea of Japan during winter, although the scale is much larger. This enables the author to apply a scenario similar to triggered lightning for winter thunderstorms, based on EHD concepts, electric reconnection and critical velocity. Then, the following general principle applies to such luminous events: a region of electric cusp can become a source-origin of whole processes and any relevant perturbation to the cusp region tends to trigger electric reconnection, leading to cloud-to-ground, cloud-to-cloud, and cloud-to-ionosphere discharges. Accordingly, it is inferred that upper atmospheric flashes should be originated along the topside cusp boundary of positive polarity in the following processes. First, a positive-to-ground discharge occurs along the bottomside cusp boundary, following electric reconnection by some perturbations into the bottomside cusp such as spider lightning intra-cloud discharges.