The source altitude, electric current, and intrinsic brightness of terrestrial gamma ray flashes

Cummer, Steven A.; Briggs, M. S.; Dwyer, J. R.; Xiong, S. L.; Connaughton, V.; Fishman, G. J.; Lu, Gaopeng; Lyu, Fanchao; Solanki, Rahulkumar

doi:10.1002/2014gl062196

Cited by 92 publications

(181 citation statements)

References 36 publications

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“…On the other hand, tropopause height seems to play an important, but not dominant role, in the TGF geographic distribution [ Smith et al , ] and the TGF sample cannot be fully considered a subset of the lightning stroke sample, as there exist some regional discrepancies in the two distributions [ Fuschino et al , ]. Investigations on the intrinsic brightness of TGFs also reveal that the source region should be placed in the interior of the thunderstorm, between the two main charge layers [ Cummer et al , ].…”

Section: Introductionmentioning

confidence: 99%

Detection of multiple terrestrial gamma‐ray flashes from thunderstorm systems

et al. 2016

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Since their discovery, Terrestrial Gamma ray Flashes (TGFs) exhibited an evident correlation with thunderstorms and lightning activity. The fleeting nature of these events and the heavy absorption of gamma rays in the lowest atmospheric layers severely hamper the observation of this phenomenon, making us reveal just a small fraction of a probably much wider population. As each thunderstorm produces a large amount of lightning discharges during its lifetime, it is reasonable that even a large amount of TGFs are produced during the same event. However, detection of multiple TGFs coming from the same storm is difficult to perform, as it requires the constant monitoring of a spatially limited geographic region: this is not an easy task to perform for satellites on high‐inclination orbits that make them experience nonnegligible latitudinal shifts at each orbital passage over a certain region, preventing the monitoring of a limited geographic region throughout successive overpasses. In this perspective, the quasi‐equatorial (2.5°) orbit of the Astrorivelatore Gamma ad Immagini LEggero (AGILE) satellite ensures a minimal latitudinal shift when flying over the same region at successive passages, allowing for the follow‐up of thunderstorms in time. We exploit this feature of the AGILE satellite to search for multiple TGFs coming from the same geographic region and, in particular, from the same thunderstorm. We carry out this search on the AGILE TGF database (2009–2016), ending up with a sample of 79 systems producing more than one TGF, both during the same overpass and up to four overpasses after. Data acquired by geostationary meteorological satellites and cross correlation with radio sferics detected by World Wide Lightning Location Network are used to support this investigation. The AGILE satellite for the first time clearly establishes the multiple occurrences of TGFs from convective thunderstorms, both on timescales of minutes to several hours.

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Section: Introductionmentioning

confidence: 99%

Detection of multiple terrestrial gamma‐ray flashes from thunderstorm systems

et al. 2016

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“…The magnetic field on Earth is rather complex and varies both by latitude and altitude. However, since we are considering the case of typical thunderstorm altitudes of 12–15 km [ Dwyer and Smith , ; Cummer et al , ], the magnetic field does not change significantly from the value at the surface. In this paper, we explored the most extreme case, namely, when B ⊥ E .…”

Section: Discussionmentioning

confidence: 99%

Magnetic field modification to the relativistic runaway electron avalanche length

2016

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This paper explores the impact of the geomagnetic field on the relativistic runaway electron avalanche length, λe−. Coleman and Dwyer (2006) developed an analytical fit to Monte Carlo simulations using the Runaway Electron Avalanche Model. In this work, we repeat this process but with the addition of the geomagnetic field in the range of [100,900]/n μT, where n is the ratio of the density of air at altitude to the sea level density. As the ambient electric field approaches the runaway threshold field (Eth≈284 kV/m sea level equivalent), it is shown that the magnetic field has an impact on the orientation of the resulting electron beam. The runaway electrons initially follow the vertically oriented electric field but then are deflected in the v × B direction, and as such, the electrons experience more dynamic friction due to the increase in path length. This will be shown to result in a difference in the avalanche length from the case where B = 0. It will also be shown that the average energy of the runaway electrons will decrease while the required electric field to produce runaway electrons increases. This study is also important in understanding the physics of terrestrial gamma ray flashes (TGFs). Not only will this work impact relativistic feedback rates determined from simulations, it may also be useful in studying spectroscopy of TGFs observed from balloon and aircraft measurements. These models may also be used in determining beaming properties of TGFs originating in the tropical regions seen from orbiting spacecraft.

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“…Typical baseline to wavelength ratios vary in the range from ∼10 to 10,000 (e.g., compare Tables 1 and 2 in Nag et al [2015]). One novel application of these lightning detection networks is the remote sensing of high peak current in-cloud lightning discharges and initial stepped leaders that might be associated with the generation of terrestrial gamma ray flashes [Lyu et al, 2016Cummer et al, 2015Cummer et al, , 2014Stanley et al, 2006]. More recently, lightning location networks with baseline to wavelength ratios ∼1-2 were developed Mezentsev and Füllekrug, 2013;Bitzer et al, 2013].…”

Section: Introductionmentioning

confidence: 99%

Mapping lightning in the sky with a mini array

Füllekrug

Liu

Koh

et al. 2016

Geophysical Research Letters

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Mini arrays are commonly used for infrasonic and seismic studies. Here we report for the first time the detection and mapping of distant lightning discharges in the sky with a mini array. The array has a baseline to wavelength ratio ∼4.2·10−2 to record very low frequency electromagnetic waves from 2 to 18 kHz. It is found that the mini array detects ∼69 lightning pulses per second from cloud‐to‐ground and in‐cloud discharges, even though the parent thunderstorms are ∼900–1100 km away and a rigorous selection criterion based on the quality of the wavefront across the array is used. In particular, lightning pulses that exhibit a clockwise phase progression are found at larger elevation angles in the sky as the result of a birefringent subionospheric wave propagation attributed to ordinary and extraordinary waves. These results imply that long range lightning detection networks might benefit from an exploration of the wave propagation conditions with mini arrays.

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The source altitude, electric current, and intrinsic brightness of terrestrial gamma ray flashes

Cited by 92 publications

References 36 publications

Detection of multiple terrestrial gamma‐ray flashes from thunderstorm systems

Detection of multiple terrestrial gamma‐ray flashes from thunderstorm systems

Magnetic field modification to the relativistic runaway electron avalanche length

Mapping lightning in the sky with a mini array

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