Characteristics of Radio Emissions Associated With Terrestrial Gamma‐Ray Flashes

Mailyan, B.; Nag, A.; Murphy, Martin J.; Briggs, M. S.; Dwyer, J. R.; Rison, W.; Krehbiel, P. R.; Boggs, L.; Bozarth, A.; Cramer, E. S.; Roberts, O. J.; Stanbro, M.; Rassoul, H. K.

doi:10.1029/2018ja025450

Cited by 28 publications

(24 citation statements)

References 63 publications

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“…But the TGF source altitude range of 10–15 km is consistent with all of the events. Note that the TGF source altitude range of 10.6−13.9 km in case 6 is consistent with the LMA VHF source altitudes reported by Mailyan et al () and Lyu et al () for the same event.…”

Section: Analysis and Resultssupporting

confidence: 90%

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Low Frequency Radio Pulses Produced by Terrestrial Gamma‐Ray Flashes

Cummer

Lyu

et al. 2019

Geophysical Research Letters

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Do terrestrial gamma‐ray flashes (TGFs) produce their own radio signatures? To explore this question, we analyze TGF data from the Fermi Gamma‐ray Burst Monitor, independent lightning geolocation data from the National Lightning Detection Network, and low‐frequency (LF) magnetic field waveforms, to determine the relationship between TGF generation and LF waveforms. LF waveforms associated with six TGFs are found to contain a clear and isolated slow pulse (~80‐μs duration) within a sequence of multiple fast pulses (<10‐μs risetime). We find that the slow LF pulse is produced simultaneously with the observed gamma rays, with an uncertainty as small as 7 μs. Simultaneity implies a consistent TGF source altitude range of approximately 10–15 km, which is consistent with previous estimates. These findings provide important evidence that the slow LF pulse, when observed, is associated with TGF production and perhaps produced by the electron acceleration itself.

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Section: Analysis and Resultssupporting

confidence: 90%

“…Fermi GBM detected a TGF at 21:23:43.910235 UT on 4 September 2015 (also discussed in Mailyan et al, , and Lyu et al, ). The Fermi geographic footprint was 24.69 °N, −83.06 °E while the satellite altitude was 541.55 km.…”

Section: Analysis and Resultsmentioning

confidence: 78%

Low Frequency Radio Pulses Produced by Terrestrial Gamma‐Ray Flashes

Cummer

Lyu

et al. 2019

Geophysical Research Letters

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“…In an effort to understand how EIPs are produced and gain insight into TGF generation, we have presented sub-microsecond VHF radio mapping of an EIP, providing over an order of magnitude finer temporal detail than previously reported TGF-related VHF observations (Lu et al, 2010;Lyu et al, 2016Lyu et al, , 2018Mailyan et al, 2018). Given that EIPs can serve as proxy for a subpopulation of TGFs (Cummer et al, 2017;Lyu et al, 2016), and that the observed EIP sferic developed independently from the VHF emissions generally associated with streamer activity (Liu et al, 2019;Rison et al, 2016;Shi et al, 2016Shi et al, , 2019, our study provides strong evidence that the EIP sferic was not produced by conventional lightning processes (i.e., streamers and leaders), but by the relativistic electrons and associated ionization of a TGF-producing discharge.…”

Section: Discussionmentioning

confidence: 99%

Radio Interferometer Observations of an Energetic in‐Cloud Pulse Reveal Large Currents Generated by Relativistic Discharges

et al. 2020

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The production mechanism for terrestrial gamma ray flashes (TGFs) is not entirely understood, and details of the corresponding lightning activity and thunderstorm charge structure have yet to be fully characterized. Here we examine sub-microsecond VHF (14-88 MHz) radio interferometer observations of a 247-kA peak-current EIP, or energetic in-cloud pulse, a reliable radio signature of a subset of TGFs. The EIP consisted of three high-amplitude sferic pulses lasting ≃60 μs in total, which peaked during the second (main) pulse. The EIP occurred during a normal-polarity intracloud lightning flash that was highly unusual, in that the initial upward negative leader was particularly fast propagating and discharged a highly concentrated region of upper-positive storm charge. The flash was initiated by a high-power (46 kW) narrow bipolar event (NBE), and the EIP occurred about 3 ms later after ≃3 km upward flash development. The EIP was preceded ≃200 μs by a fast 6 × 10 6 m/s upward negative breakdown and immediately preceded and accompanied by repeated sequences of fast (10 7-10 8 m/s) downward then upward streamer events each lasting 10 to 20 μs, which repeatedly discharged a large volume of positive charge. Although the repeated streamer sequences appeared to be a characteristic feature of the EIP and were presumably involved in initiating it, the EIP sferic evolved independently of VHF-producing activity, supporting the idea that the sferic was produced by relativistic discharge currents. Moreover, the relativistic currents during the main sferic pulse initiated a strong NBE-like event comparable in VHF power (115 kW) to the highest-power NBEs.

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“…Although the relativistic runaway electron avalanche process (Dwyer, 2003;Gurevich et al, 1992) is widely accepted, additional mechanisms such as the thermal electron runaway model (Carlson et al, 2010;Celestin & Pasko, 2011) or the relativistic feedback processes (Dwyer, 2003(Dwyer, , 2008(Dwyer, , 2012 are thought to be required. Besides gamma-ray observations, ground-based radio-frequency (RF) measurements provide insights into the TGF-producing mechanism (Abbasi et al, 2018;Cummer et al, 2014Cummer et al, , 2015Lu et al, 2010;Lyu et al, 2016;Mailyan et al, 2018). Source location and altitude estimated by RF measurements are useful to investigate the total number of avalanche electrons in TGFs (Dwyer & Cummer, 2013;Cummer et al, 2014Cummer et al, , 2015Mailyan et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

High Peak‐Current Lightning Discharges Associated With Downward Terrestrial Gamma‐Ray Flashes

et al. 2020

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During 2017–2018 winter operation of the Gamma‐Ray Observation of Winter Thunderclouds experiment in Japan, two downward terrestrial gamma‐ray flashes (TGFs) that triggered atmospheric photonuclear reactions were detected. They took place during winter thunderstorms on 5 December 2017 and 9 January 2018 at Kanazawa, Ishikawa Prefecture, Japan. Each event coincided with an intracloud/intercloud discharge, which had a negative‐polarity peak current higher than 150 kA. Their radio waveforms in the low‐frequency band are categorized as a distinct lightning type called “energetic in‐cloud pulse” (EIP). Negative‐polarity EIPs have been previously suggested to be highly associated with downward TGFs, and the present observations provide evidence of the correlation between them for the first time. Furthermore, both of the downward TGFs followed “gamma‐ray glows,” minute‐lasting high‐energy emissions from thunderclouds. It is suggested that the negative EIPs took place with downward propagating negative leaders or upward positive ones developed in highly electrified regions responsible for the gamma‐ray glows.

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Characteristics of Radio Emissions Associated With Terrestrial Gamma‐Ray Flashes

Cited by 28 publications

References 63 publications

Low Frequency Radio Pulses Produced by Terrestrial Gamma‐Ray Flashes

Low Frequency Radio Pulses Produced by Terrestrial Gamma‐Ray Flashes

Radio Interferometer Observations of an Energetic in‐Cloud Pulse Reveal Large Currents Generated by Relativistic Discharges

High Peak‐Current Lightning Discharges Associated With Downward Terrestrial Gamma‐Ray Flashes

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