Magnetic field modification to the relativistic runaway electron avalanche length

Cramer, E. S.; Dwyer, J. R.; Rassoul, H. K.

doi:10.1002/2016ja022891

Cited by 4 publications

(6 citation statements)

References 27 publications

(59 reference statements)

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“…is lower than ∼50 μT for latitudes below 30°(e.g., Finlay et al, 2010), which encompasses Fermi's orbit. Cramer et al (2016) have shown that the dynamics of RREAs (e.g., RREA rates, characteristic lengths, and speed) would not be significantly modified in such low magnetic fields. Moreover, the electric field threshold above which RREAs can develop is known to be E th ¼ 2.8×N/ N 0 kV/cm (e.g., Dwyer et al, 2012), where N is the local air density and N 0 is the air density at ground level.…”

Section: Deviation Of Rreas In Homogeneousmentioning

confidence: 99%

“…This is presumably the reason that the effect of geomagnetic field on RREAs has seldom been studied, with notable exceptions. Lehtinen et al (1999) and Cramer et al (2016) have quantified RREA rates in the presence of a magnetic field. From these papers, it can be seen that the strength of the geomagnetic field (<50 μT) is not sufficient to have a significant effect on RREA rates.…”

Section: Introductionmentioning

confidence: 99%

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Geomagnetic Deviation of Relativistic Electron Beams Producing Terrestrial Gamma Ray Flashes

et al. 2020

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In this work, we investigate the effect of the geomagnetic field on terrestrial gamma ray flashes (TGFs). Although this effect should be relatively weak for a single event, for example compared to the effect of the electric field orientation in the source region, it must be systematically present. Indeed, we show that a statistically significant excess of TGFs is detected to the east of their presumed lightning source by Fermi-Gamma-ray Burst Monitor (GBM). The corresponding eastward deviation is found to be likely greater than 0.1°in longitude, which is consistent with the expected effect of the geomagnetic field on relativistic runaway electron beams producing TGFs. Using analytical and numerical means, we show that the geomagnetic deviation can be used to estimate the magnitude of the electric field in TGF source regions. The electric field magnitudes we obtain are consistent with those necessary to drive relativistic runaway electron avalanches (RREAs).

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Section: Deviation Of Rreas In Homogeneousmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Geomagnetic Deviation of Relativistic Electron Beams Producing Terrestrial Gamma Ray Flashes

et al. 2020

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“…The electric fields used in the simulation were normalized by the threshold value for which electrons run away, E th = 286 kV/m. This value is higher than the break even field ( E b = 215 kV/m), which is the strength where minimum ionizing electrons lose energy [ Cramer et al , ]. Note that the calculations to obtain these values are done for an atomic number density of air equal to 5.39 × 10 25 atoms/m 3 .…”

Section: Model Descriptionmentioning

confidence: 99%

A simulation study on the electric field spectral dependence of thunderstorm ground enhancements and gamma ray glows

et al. 2017

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We have done a thorough simulation analysis on the variability of the photon spectra produced with (due to Relativistic Runaway Electron Avalanche—RREA) and without (Modification of Spectra) the avalanche multiplication process. Despite some measurements obviously showing a variability of the spectra, numerous theoretical studies consider RREA spectrum independent on the electric field. However, analytical calculations by Cramer et al. (2014) have shown that RREA spectrum under low electric fields is not constant and stops being exponential. Using the Relativistic Electron Avalanche Model code, we model various layouts of the electric field configuration and study the predicted photon spectra. The primary focus of the present paper is to study the photon energy spectra, as gamma rays are more often observed by ground‐based detectors. The simulation analysis of photon spectra potentially can help to deduce electric fields in thunderclouds.

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“…REAM is a three-dimensional Monte Carlo simulation of the relativistic runaway electron avalanche (also referred to as runaway breakdown), including electric and magnetic fields (Dwyer, 2003(Dwyer, , 2007Cramer et al, 2016). This code is inspired by earlier work by Lehtinen et al (1999) and takes accurately into account all the important interactions involving runaway electrons, including energy losses through ionisation, atomic excitation and Møller scattering.…”

Section: Reammentioning

confidence: 99%

Evaluation of Monte Carlo tools for high-energy atmospheric physics II: relativistic runaway electron avalanches

et al. 2018

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The emerging field of high-energy atmospheric physics studies how high-energy particles are produced in thunderstorms, in the form of terrestrial γ -ray flashes and γ -ray glows (also referred to as thunderstorm ground enhancements). Understanding these phenomena requires appropriate models of the interaction of electrons, positrons and photons with air molecules and electric fields. We investigated the results of three codes used in the community -Geant4, GRanada Relativistic Runaway simulator (GRRR) and Runaway Electron Avalanche Model (REAM) -to simulate relativistic runaway electron avalanches (RREAs). This work continues the study of Rutjes et al. (2016), now also including the effects of uniform electric fields, up to the classical breakdown field, which is about 3.0 MV m −1 at standard temperature and pressure.We first present our theoretical description of the RREA process, which is based on and incremented over previous published works. This analysis confirmed that the avalanche is mainly driven by electric fields and the ionisation and scattering processes determining the minimum energy of electrons that can run away, which was found to be above ≈ 10 keV for any fields up to the classical breakdown field.To investigate this point further, we then evaluated the probability to produce a RREA as a function of the initial electron energy and of the magnitude of the electric field. We found that the stepping methodology in the particle simulation has to be set up very carefully in Geant4. For ex-ample, a too-large step size can lead to an avalanche probability reduced by a factor of 10 or to a 40 % overestimation of the average electron energy. When properly set up, both Geant4 models show an overall good agreement (within ≈ 10 %) with REAM and GRRR. Furthermore, the probability that particles below 10 keV accelerate and participate in the high-energy radiation is found to be negligible for electric fields below the classical breakdown value. The added value of accurately tracking low-energy particles (< 10 keV) is minor and mainly visible for fields above 2 MV m −1 .In a second simulation set-up, we compared the physical characteristics of the avalanches produced by the four models: avalanche (time and length) scales, convergence time to a self-similar state and energy spectra of photons and electrons. The two Geant4 models and REAM showed good agreement on all parameters we tested. GRRR was also found to be consistent with the other codes, except for the electron energy spectra. That is probably because GRRR does not include straggling for the radiative and ionisation energy losses; hence, implementing these two processes is of primary importance to produce accurate RREA spectra. Including precise modelling of the interactions of particles below 10 keV (e.g. by taking into account molecular binding energy of secondary electrons for impact ionisation) also produced only small differences in the recorded spectra.

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Magnetic field modification to the relativistic runaway electron avalanche length

Cited by 4 publications

References 27 publications

Geomagnetic Deviation of Relativistic Electron Beams Producing Terrestrial Gamma Ray Flashes

Geomagnetic Deviation of Relativistic Electron Beams Producing Terrestrial Gamma Ray Flashes

A simulation study on the electric field spectral dependence of thunderstorm ground enhancements and gamma ray glows

Evaluation of Monte Carlo tools for high-energy atmospheric physics II: relativistic runaway electron avalanches

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