Collaborative Research: Physics Based Modeling of Blue Jets

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Narrow cones of blue light that propagate upward from the top of a thundercloud were discovered during the Sprites94 aircraft campaign. Two types of blue jets (BJ) have been observed. The brief upward jets, which propagate only a few km and terminate below 26 km, were dubbed blue starters (BS), while so-called gigantic blue jets (GBJ) propagate into the mesosphere/lower ionosphere. It is widely accepted that BJ?s are produced by an upward propagating leader from thunderstorms. Some attempts have been made to describe the leader formation, including recent model of bipolar BJ. However, despite substantial progress in the theoretical understanding of this complicated phenomenon, significant puzzles remain. In fact, two outstanding problems are still unresolved and both are relevant to the laboratory leaders, as well as to the leaders formed by lightning. Namely, which mechanism governs the low propagation velocity of the leader, and how a self-consistent electric field in the streamer zone of a leader is formed. This research will focus on quantitative modeling of Blue Jets/Blue Starters/Gigantic Blue Jets. It will combine two major models, the first is an analytical and numerical study of current contraction, which determines transformation of a streamer flash into a leader, and which governs slow propagation velocity of BJ?s. The second is a model of the average electric field formed by a group of streamers in the streamer zone of a leader, which determines the BJ formation. The theoretical study will be complemented by the table top experiments that could be used for validation of the existing models. The ground based and satellite-borne optical and ultraviolet observations will attempt to validate the model predictions. Understanding the physics of BJ/BS/GBJ is not only a frontier scientific topic, but it could provide a mechanism for direct transient coupling between the ionosphere and stratosphere with implication to the global electric circuit. Potential applications include: extending fundamental knowledge in the physics of gas discharge and weakly ionized plasma by applying our model to laboratory experiments of streamer and leader breakdown, and influencing the design of powerful lasers and plasma chemical reactors through a quantitative understanding of current contraction. The program will support the education and training of the University of Maryland students in this multidisciplinary field, combining aspects of theoretical and computational plasma physics as well as gas dynamics. The study will promote collaboration between the academia and industry. It also involves broad international collaboration between Princeton University, the University of Maryland, and leading scientists from the Russian Academy of Sciences.