CEDAR: Quantitative Measurements of Lightning-Mesosphere Interactions from Remote Electromagnetic Fields

Duke University, Durham NC

Investigators

Abstract

The investigators will analyze existing electromagnetic field and video data associated with transient luminous events (TLEs) in the middle atmosphere to quantitatively measure parameters related to processes that are directly related to existing models. Sprites and other mesospheric TLEs are a visual manifestation of the direct coupling between the troposphere and upper atmosphere. The study of these phenomena has reached the point where observations and qualitative understanding are probably sufficient to begin realistically quantifying their micro- and macroscale effects and their significance in the larger mesosphere-lower thermosphere-ionosphere (MLTI) system. Quantitative understanding of TLE internal processes is a necessary first step towards understanding the effects of TLE-related processes on the MLTI system; without understanding in detail what happens inside them, it is nearly impossible to extrapolate their large-scale effects. And there are aspects of TLE phenomena that are not explained by present models, suggesting that understanding of TLE internal processes may not be sufficient to evaluate these effects. The study will focus on the following four science questions: Do influences beyond the lightning-driven electromagnetic fields, such as gravity waves and meteoritic dust, play a role in TLE-generating processes? What electromagnetic field strengths are required to initiate TLE-generating mesospheric processes? Is there an asymmetry in TLE production between positive and negative polarity cloud-to-ground lightning discharges? Is there an identifiable difference in optical emissions or driving lightning parameters between sprites that do and do not contain sprite current? Answering these questions will substantially improve quantitative understanding of lightning-ionosphere coupling processes and, consequently, the ability to predict their larger scale effects. The study will make use of past experimental measurements as well as observations to be made with existing instrumentation. Sprites and TLEs are not only visually spectacular. They are also manifestations of the complex electrical processes that exist in thunderstorms and link the lower atmosphere to the upper atmosphere.