Now showing items 1-12 of 12

    • The angular distribution of energetic electron and X-ray emissions from triggered lightning leaders 

      Schaal, M.M.; Dwyer, Joseph R.; Rassoul, Hamid K.; Hill, Jonathan David; Jordan, Douglas M.; Uman, Martin A. (2013-10-27)
      We investigate individual X-ray bursts from lightning leaders to determine if energetic electrons at the source (and hence X-rays) are emitted isotropically or with some degree of anisotropy. This study was motivated by ...
    • "Chaotic" dart leaders in triggered lightning: Electric fields, X-rays, and source locations 

      Hill, Jonathan D.; Uman, Martin A.; Jordan, Douglas M.; Dwyer, Joseph R.; Rassoul, Hamid K. (2012)
      We present the first published observations of "chaotic" dart leaders in triggered-lightning discharges. We examine four leaders that exhibited "chaotic" electric field derivative (dE/dt) signatures in their final 10 to ...
    • Co-location of lightning leader x-ray and electric field change sources 

      Howard, John J.; Uman, Martin A.; Dwyer, Joseph R.; Hill, Dustin; Biagi, Christopher J.; Saleh, Ziad H.; Jerauld, Jason E.; Rassoul, Hamid K. (2008-07-11)
      Using an eight-station time of arrival (TOA) network composed of NaI(Tl) scintillation detectors and wideband electric field derivative (dE/dt) antennas covering approximately 1 km² on the ground, we have located both the ...
    • Do cosmic ray air showers initiate lightning?: A statistical analysis of cosmic ray air showers and lightning mapping array data 

      Hare, B. M.; Dwyer, Joseph R.; Winner, Lawrence H.; Uman, Martin A.; Jordan, Douglas M.; Kotovsky, D. A.; Caicedo, J. A.; Wilkes, R. A.; Carvalho, Filipa L.; Rassoul, Hamid K. (2017)
      It has been argued in the technical literature, and widely reported in the popular press, that cosmic ray air showers (CRASs) can initiate lightning via a mechanism known as relativistic runaway electron avalanche (RREA), ...
    • High-speed X-ray images of triggered lightning dart leaders 

      Dwyer, Joseph R.; Schaal, M. M.; Rassoul, Hamid K.; Uman, Martin A.; Jordan, Douglas M.; Hill, Dustin (2011-10-26)
      We present the first high-time resolution two-dimensional images of X-ray emissions from lightning. The images were recorded at a rate of 10 million per second using a new pinhole-type camera, located 44 m from rocket-and-wire- ...
    • Observations of stepping mechanisms in a rocket-and-wire triggered lightning flash 

      Biagi, Christopher J.; Uman, Martin A.; Jordan, Douglas M.; Rakov, Vladimir A.; Dwyer, Joseph R.; Hill, Jonathan D. (2010-12-14)
      We present 10 high-speed video images that depict the bottom 150 m of a downward-negative, dart-stepped leader in a rocket-and-wire triggered flash, recorded at 240 kiloframes per second (4.17 μs frame integration time), ...
    • Properties of the X-ray emission from rocket-triggered lightning as measured by the Thunderstorm Energetic Radiation Array (TERA) 

      Saleh, Ziad H.; Dwyer, Joseph R.; Howard, Joseph S.; Uman, Martin A.; Bakhtiari, Mohammad Reza; Concha, D; Stapleton, Michael V.; Hill, Dustin; Biagi, Christopher J.; Rassoul, Hamid K. (2009)
      The Thunderstorm Energetic Radiation Array (TERA) is located at the University of Florida, Florida Tech International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida. The array includes forty-five ...
    • Remote measurements of thundercloud electrostatic fields 

      Dwyer, Joseph R.; Uman, Martin A.; Rassoul, Hamid K. (2009-05-16)
      Analytical and numerical models of the radio frequency emissions produced by relativistic runaway electron avalanches initiated by cosmic ray extensive air showers are presented. It is found that single-point measurements ...
    • RF and X-ray source locations during the lightning attachment process 

      Howard, Joseph S.; Uman, Martin A.; Biagi, Christopher J.; Hill, Dustin; Jerauld, Jason E.; Rakov, Vladimir A.; Dwyer, Joseph R.; Saleh, Ziad H.; Rassoul, Hamid K. (2010-03-18)
      Using an eight-station array of electric field derivative (dE/dt) sensors and colocated NaI X-ray detectors, we have obtained 3-D RF source locations during the leaders and attachment processes of three first strokes ...
    • Spatial and energy distributions of X-ray emissions from leaders in natural and rocket triggered lightning 

      Schaal, Meagan M.; Dwyer, Joseph R.; Saleh, Ziad H.; Rassoul, Hamid K.; Hill, Jonathan D.; Jordan, Douglas M.; Uman, Martin A. (2012)
      Energetic radiation is known to be produced by lightning. To investigate these emissions, ground-based observations are being conducted at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, ...
    • X-ray bursts associated with leader steps in cloud-to-ground lightning 

      Dwyer, Joseph R.; Rassoul, Hamid K.; Dayeh, M. A.; Caraway, Lee; Chrest, A.; Wright, Brian F.; Kozak, E.; Jerauld, J.; Uman, Martin A.; Rakov, V. (2005-01-04)
      X-ray and electric field measurements were made during five nearby negative natural lightning strikes in north central Florida during the summer of 2004. The observed X-ray emission typically was detected ∼1 ms before the ...
    • X-ray bursts produced by laboratory sparks in air 

      Dwyer, Joseph R.; Rassoul, Hamid K.; Saleh, Ziad H.; Uman, Martin A.; Jerauld, J.; Plumer, J. Anderson (2005-10-22)
      X-ray observations were made during fourteen 1.5 to 2.0 m high-voltage discharges in air produced by a 1.5 MV Marx circuit. All 14 discharges generated x-rays in the ∼30 to 150 keV range. The x-rays, which arrived in ...