Ningyu Liu

Victor P Pasko9
Hamid K Rassoul9
Joseph R Dwyer7
9Victor P Pasko
9Hamid K Rassoul
7Joseph R Dwyer
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[1] Modeling studies indicate that double-headed streamers originating from single electron avalanches in lightning-driven quasi-static electric fields at mesospheric altitudes accelerate and expand, reaching transverse scales from tens to a few hundreds of meters and propagation speeds up to one tenth of the speed of light, in good agreement with recent(More)
A novel immersed boundary velocity correction–lattice Boltzmann method is presented and validated in this work by its application to simulate the two-dimensional flow over a circular cylinder. The present approach is inspired from the conventional immersed boundary method (IBM). In the conventional IBM, the effect of rigid body on the surrounding flow is(More)
[1] The time dependent optical emission model developed by Liu and Pasko (2004) is applied to studies of far-UV emissions of sprite streamers due to N 2 Lyman-Birge-Hopfield (LBH) band system. Modeling results indicate that the LBH emissions of sprite streamers at 70 km are generally stronger by up to a factor of 10 than those from the first negative band(More)
Recent advances in development of photoionization models in air based on radiative transfer and Helmholtz equations open new perspectives for efficient solution of nonthermal gas discharge problems involving complex geometries. Many practical applications require accurate modeling of streamer discharges developing in weak electric fields, in which the(More)
[1] A two-dimensional fluid model with multiple charged species is developed for simulating the ionospheric responses to the lightning quasi-static electric (QE) field. In addition to electrons, the model takes into account four symbolic ion species and O À ions that are considered separately to investigate the role of the fast electron detachment process(More)
This Letter reports a modeling study on the formation of streamer discharges from an isolated ionization column under subbreakdown condition. Numerical simulations show that positive streamers are able to form from the tip of an ionization column in a uniform applied electric field well below the breakdown threshold field. However, even when the applied(More)
[1] Three intensity ratios of the second positive band system of N 2 to N 2 LBH band system, the first negative band system of N 2 + , and the first positive band system of N 2 are obtained separately from sprite streamer modeling and from measurements by ISUAL instrument on FORMOSAT-2 satellite. The direct comparison between the obtained ratios indicates(More)
  • Burcu C Kosar, Ningyu Liu, Hamid K Rassoul, B C Kosar, N Liu, H K Rassoul
  • 2012
[1] This paper reports a modeling study on sprite streamer formation at subbreakdown conditions, i.e., the initiation of sprite streamers in a lightning field below the breakdown threshold field E k. Successful formation of streamers is observed for a variety of electric fields with the lowest field of 0.3E k when an appropriate ionization column is(More)
  • Ningyu Liu, Joseph R Dwyer, N Y Liu, J R Dwyer
  • 2013
[1] This paper reports a modeling study of terrestrial gamma ray flashes (TGFs) produced by relativistic feedback discharges. Terrestrial gamma ray flashes are intense energetic radiation originating from the Earth's atmosphere that has been observed by spacecraft. They are produced by bremsstrahlung interactions of energetic electrons, known as runaway(More)