Lightning is one of the worst natural hazards, killing more people in the USA on average than hurricanes or tornadoes and causing substantial damage to property and sensitive equipment. In spite of decades of study, we still do not understand exactly what physical mechanism causes the first spark of a lightning flash, how that spark grows into a conducting path (the lightning "channel"), or how the channel moves through cloudy and clear air.
By using a unique array of sensors, this project aims to gather new information about lightning initiation and lightning propagation to help explain how these two fundamental aspects of lightning may work. The measurements will be made at the NASA Kennedy Space Center (KSC) in Florida. Lightning is especially frequent at KSC, causes expensive operational delays, and sometimes damages sensitive rocket and shuttle vehicles and/or facilities.
Intellectual merits: This NSF project is an extension of a recently completed NSF EArly-concept Grant for Exploratory Research award - "EAGER Multi-Frequency Studies of Lightning Initiation and Propagation" - and builds on the successful results of that initial award. The completed EAGER project used lightning observations with five different measurement systems. The enhanced observational scheme for this NSF project will expand EAGER project with eight systems to observe lightning processes: (1) "slow" antennas, (2) "fast" antennas, (3) a network of seven crossed-loop magnetic sensors, (4) the KSC electric field mill network, (5) the KSC Lightning Detection And Ranging (LDAR) system, (6) the KSC Cloud-to-Ground Lightning Surveillance System (CGLSS), (7) high-speed video cameras (at 54,000 frames/second), (8) VHF radio emissions, and (9) fast electric field changes (dE/dt). All nine sensors look at electromagnetic changes caused by lightning as it accelerates and moves charge; the sensors operate across a wide and partially overlapping range of electromagnetic frequencies.
The various sensors respond to different parts of a flash: some parts are only a few meters in length while others are as long as a several thousand meters. There are two key features of the sensor array that will be especially useful in this new lightning investigation. First, the array will be able to determine the previously unknown locations of the long, fast electromagnetic pulses that occur during the initiation of both in-cloud and cloud-to-ground lightning flashes. Second, the high-speed video images of a propagating lightning flash will literally give us visual pictures to combine with and compare with the data from the other 8 sensors. Overall, the intellectual merit of the project stems from combining the data from these nine sensors to provide new insights into how lightning initiation and lightning propagation work.
Broader impacts: Developing a better understanding of the mechanisms behind a particular hazard (lightning, in this case) can lead to new and improved ways of protecting people and property from that hazard. Lightning protection systems are primarily based in science, and determining how lightning initiates and propagates may reveal new ways to protect objects on the ground and in the air.
This project will also be important for the development and training of several new scientists, including one graduate student pursuing a Ph. D. degree, two other graduate students just beginning their training, and two undergraduate physics students interested in being involved in scientific research. The training involves techniques that are specific to electromagnetic measurements of lightning as well as techniques that are generally applicable in many situations (including computer programming, computer control of instruments, computer modeling, etc.). The results of this project will also be broadly disseminated in the peer-reviewed literature.
