Elementary processes capable of producing neutrons in thunderstorms are analyzed. Efficiency is e... more Elementary processes capable of producing neutrons in thunderstorms are analyzed. Efficiency is evaluated of nuclear fusion, photonuclear reaction, electrodisintegration, and reaction inverse to the β-decay. An extraordinary strong electric field is required for nuclear fusion to occur in a lightning channel. The inverse to β-decay reactions are too weak. The generation of neutrons in a thunderstorm is connected with photonuclear and, to a lesser degree, with electrodisintegration reactions.
A new empirical model of the plasmapause location has been developed using density data from the ... more A new empirical model of the plasmapause location has been developed using density data from the plasma wave receiver onboard the CRRES spacecraft for nearly 1000 orbits. The ''plasmapause'' is identified here as the innermost sharp gradient in density (change of a factor of 5 in <0.5 L). Such a sharp gradient was observed on 73% of the CRRES inbound and outbound orbits that returned data. The plasmapause location is expressed as a linear function of Kp (previous 12 hour maximum) and local time. The model gives the linear best fit location of the plasmapause as well as the standard deviations of the model parameters. We found a slight noon-midnight asymmetry with the plasmapause located on average an L shell farther from the Earth at midnight than in the noon sector. This is in the opposite sense to the noon-midnight asymmetry found previously. Significant variability (with standard deviations up to +/À 1 L shell) in the plasmapause location is seen and suggests that though the mean plasmapause is roughly circular, the instantaneous plasmapause has significant time variable localized structure at all local times but most especially in the duskside sector.
, the Airborne Detector for Energetic Lightning Emissions (ADELE), an array of six gamma-ray dete... more , the Airborne Detector for Energetic Lightning Emissions (ADELE), an array of six gamma-ray detectors, detected a brief burst of gamma rays while flying aboard a Gulfstream V jet near two active thunderstorm cells. The duration and spectral characteristics of the event are consistent with the terrestrial gamma ray flashes (TGFs) seen by instruments in low Earth orbit. A long-duration, complex +IC flash was taking place in the nearer cell at the same time, at a distance of ∼10 km from the plane. The sferics that are probably associated with this flash extended over 54 ms and included several ULF pulses corresponding to charge moment changes of up to 30 C km, this value being in the lower half of the range of sferics associated with TGFs seen from space. Monte Carlo simulations of gamma ray propagation in the Earth's atmosphere show that a TGF of normal intensity would, at this distance, have produced a gamma ray signal in ADELE of approximately the size and spectrum that was actually observed. We conclude that this was the first detection of a TGF from an aircraft. We show that because of the distance, ADELE's directional and spectral capabilities could not strongly constrain the source altitude of the TGF but that such constraints would be possible for TGFs detected at closer range.
We report on the first search for Terrestrial Gamma-ray Flashes (TGFs) from altitudes where they ... more We report on the first search for Terrestrial Gamma-ray Flashes (TGFs) from altitudes where they are thought to be produced. The Airborne Detector for Energetic Lightning Emissions (ADELE), an array of gamma-ray detectors, was flown near the tops of Florida thunderstorms in August/September 2009. The plane passed within 10 km horizontal distance of 1213 lightning discharges and only once detected a TGF. If these discharges had produced TGFs of the same intensity as those seen from space, every one should have been seen by ADELE. Separate and significant nondetections are established for intracloud lightning, negative cloud-to-ground lightning, and narrow bipolar events. We conclude that TGFs are not a primary triggering mechanism for lightning. We estimate the TGF-to-flash ratio to be on the order of 10 −2 to 10 −3 and show that TGF intensities cannot follow the well-known power-law distribution seen in earthquakes and solar flares, due to our limits on the presence of faint events. Citation: Smith,
X-ray and electric field measurements were made during five nearby negative natural lightning str... more 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 first return stroke, during the stepped-leader phase, and had energies extending up to a few hundred keV. The X rays were produced in discrete, intense bursts emitted in coincidence with the formation of the leader steps, demonstrating unambiguously that the source of lightning X rays is closely related to the stepping process. The X-ray emission from lightning stepped leaders is found to be remarkably similar to that from lightning dart leaders, suggesting that these different types of leaders share a common mechanism. The reported observations have important implications for understanding how runaway breakdown occurs and how lightning leaders propagate.
Journal of Geophysical Research: Atmospheres, 2017
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We present observations of X-rays from laboratory sparks created in the air at atmospheric pressu... more We present observations of X-rays from laboratory sparks created in the air at atmospheric pressure by applying an impulse voltage with long (250 µs) rise-time. X-ray production in 35 and 46 cm gaps for three different electrode configurations was studied. The results demonstrate, for the first time, the production of X-rays in gaps subjected to switching impulses. The low rate of rise of the voltage in switching impulses does not significantly reduce the production of X-rays. Additionally, the timing of the X-ray occurrence suggests the possibility that the mechanism of X-ray production by sparks is related to the collision of streamers of opposite polarity.
This paper describes a method of simulating solar energetic particle propagation through the magn... more This paper describes a method of simulating solar energetic particle propagation through the magnetic fields of the solar corona and interplanetary medium. The simulation code is based on the focus transport equation of energetic particles in 3-d magnetic fields, which contains all the particle transport mechanisms, including streaming, convection, gradient/curvature drift, adiabatic focusing, pitch angle scattering by Alfvénic magnetic field fluctuations and perpendicular diffusion due to the random walk of field lines. In the simulation, particles are injected at their source in the corona, and their guiding center trajectories are calculated using stochastic differential equations. Because of the vastly different time scales of particle transport mechanisms included in the equation, we use the 4-th order Runge-Kutta method to integrate the particle streaming and adiabatic focusing terms, while the stochastic terms of pitch angle scattering and perpendicular diffusion are integrated with the Euler scheme. The model is applied to the 2017 September 10 solar energetic particle event. With perpendicular diffusion, we are able to explain SEP observations from Earth and STEREO-A. A pattern of SEP precipitation on the solar surface is also predicted.
Broadband RF Interferometric Mapping and Polarization (BIMAP) Observations of Lightning Discharges: Revealing New Physics Insights Into Breakdown Processes
• Simulated the production of energetic electron avalanches from Martian dust storms. • Found the... more • Simulated the production of energetic electron avalanches from Martian dust storms. • Found the electron avalanche characteristic length for different electric fields inside Martian dust storms. • The gamma rays can be detected by ground-based instruments and satellites orbiting Mars.
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