This award will support the development of a new monitoring array for measuring energetic radiation associated with lightning. Recent observations have shown that X-rays and gamma rays are produced by lightning, through mechanisms that are not yet understood. These investigators will install an array for measuring such radiation at the International Center for Lightning Research and Testing, a facility operated by the University of Florida. The new instruments will be placed around a tower at this facility where rockets are launched to trigger lightning. The 32-element array will measure X-rays produced by dart leaders and return strokes associated with rocket-triggered (and occasional natural) lightning, and they will also monitor gamma rays and cosmic rays (which may be deflected by the high fields present in thunderstorms). Complementary measurements already made at the Center include electric and magnetic fields, electric currents, and optical emissions. The combination of existing and new sensors will provide comprehensive characterization of the electromagnetic radiation from lightning. The new instruments, like the existing Center, will be made available to outside users and visitors.
Expected results from this development project include: new capabilities for characterizing the broad spectrum of electromagnetic radiation from lightning, including the poorly understood high-energy components; ability to collect observations that document the nature of the breakdown process involved when lightning is initiated and so constrain theoretical models of that breakdown process; and support for an emerging new community of scientists interested in these new phenomena. The installation of this instrument array at a widely used center for lightning research will advance the study of newly discovered and largely unexplored kinds of radiation produced by lightning and will also provide opportunities for many investigators to integrate these observations into their studies of the properties and nature of lightning.