The KSC studies were conducted during a two-year period between the summers of 2016-2018 to obtain additional observations of high-power NBEs, which are much more prevalent in Florida than New Mexico. The observations quickly showed that NBEs can also be produced in a manner similar to FPB, but with negative instead of positive polarity, termed fast negative breakdown (FNB).  In both cases, the breakdown was determined to be produced by a system of high-speed (typically one-tenth the speed of light or faster), non-conducting streamers, either of positive- or oppositely-directed negative polarity, despite the substantially different physics of the two polarities of streamers. Taken together with the Langmuir results, the observations have been answering the long-standing question of how lightning is initiated inside storms, in the absence of physical conductors. 

Another important outcome of the KSC studies was obtaining the first detailed observations of a lightning-caused energetic in-cloud pulse, or EIP.  EIPs rarely occur in storms but have been of substantial interest because of their exceptionally high peak currents (246 kiloamperes in this case), and their close connection with upward terrestrial gamma-ray flashes (TGFs) being detected by satellites.  Collaborative analyses of LMA, INTF, and fast electromagnetic sferic observations showed the EIP was produced by repeated relativistic discharging of a localized region of upper positive storm charge during a highly energetic intracloud flash -- one of the first direct indications of relativistic runaway electron avalanching in storms.

In particular (and surprisingly), IBPs were shown to be produced by the same type of streamer-based FNB that had just been discovered in our KSC studies.  Similar IBPs occur during the upward negative breakdown of intracloud flashes, which have also been associated with the occurrence of satellite-detected TGFs, but the correspondence was shown in significantly greater (sub-microsecond) detail by the close downward and multi-station TASD observations.  In particular, the TGFs were often initiated at the time of highly impulsive, microsecond-duration sub-pulses, which are a characteristic feature of what are termed 'classic' IBPs. In turn, this led to the sub-pulses being explained as caused by transient conducting events or 'corona flashes', whose highly impulsive occurrence launches huge numbers of relativistic electrons. That the relativistic electrons would be accelerated to gamma-level energies was determined from numerical simulations of streamer development also conducted during the grant, which showed that tens of megavolts of potential difference develops ahead of the propagating streamers, substantially increasing the electron energies.  

Whereas the initial TGFs of the Utah studies had fluences several orders of magnitude below the inferred fluences of satellite events, in the beginning of the fifth year of the Covid-extended grant (September 2021), observations were obtained of a downward TGF that was comparable in strength to satellite-detected TGFs. The TGF saturated the recording buffers of 16-18 kilometer-spaced TASD stations, while being produced in the exact same manner as lower fluence events.  Subsequent GEANT4 analyses determined the truncated fluence to exceed 10^16 primary electrons, 2--3 orders of magnitude stronger than previously-detected downward TGFs.

In addition to advancing our understanding of lightning discharge processes, the studies produced two Ph.D. dissertations, one each with collaborators at the Universities of Utah and New Hampshire, and one M.Sc. thesis at New Mexico Tech. The TASD studies also broadened the relationship between the lightning and high energy particle physics communities.