Fri, 10/19/2018 - 3:10pm to 4:00pm
DeMeritt 240
Colloquium
Prof. Ningyu Liu, Department of Physics, University of New Hampshire

Extreme Lightning

Lightning discharges come with a variety of forms, and their intensity measured in terms of current or radiated radio power spans a wide range. This colloquium will be focused on discussing our recent research work on three classes of extreme lightning. The first class is cloud-to-ground lightning flashes of a very large peak current, a few times larger than the average value. High-speed optical images will be presented to show their complex temporal and spatial properties. The second class is the most powerful source of high frequency and very high frequency electromagnetic radiation naturally occurring on Earth. They are a special class of intra-cloud discharges, termed narrow bipolar events (NBEs). Radio interferometric observations of NBEs will be shown to reveal their physical mechanism. Modeling work based on this mechanism confirms the unique radio spectrum of NBEs. The third class is called energetic in-cloud pulses (EIPs), which also have a very large peak current and have recently been demonstrated to be associated with at least a subset of terrestrial gamma ray flashes. Simulation results of the radio waves of EIPs and their impact in the lower ionosphere, causing the ionospheric phenomenon known as elves, will be presented.