Search results for "Terrestrial gamma-ray flash"
showing 9 items of 9 documents
On the timing between terrestrial gamma ray flashes, radio atmospherics, and optical lightning emission
2017
On 25 October 2012 the Reuven Ramaty High Energy Solar Spectroscope Imager (RHESSI) and the Tropical Rainfall Measuring Mission (TRMM) satellites passed over a thunderstorm on the coast of Sri Lanka. RHESSI observed a terrestrial gamma ray flash (TGF) originating from this thunderstorm. Optical measurements of the causative lightning stroke were made by the lightning imaging sensor (LIS) on board TRMM. The World Wide Lightning Location Network (WWLLN) detected the very low frequency (VLF) radio emissions from the lightning stroke. The geolocation from WWLLN, which we also assume is the TGF source location, was in the convective core of the cloud. By using new information about both RHESSI a…
Effects of dead time losses on terrestrial gamma ray flash measurements with the Burst and Transient Source Experiment
2010
[1] Measurements from the Burst and Transient Source Experiment (BATSE) instrument on the Compton Gamma Ray Observatory (CGRO) are the only ones where characteristics of single terrestrial gamma ray flashes (TGFs) have been obtained thus far. However, it has been reported that the measurements suffer from significant dead time losses which complicates the analysis and raises question about earlier BATSE studies. These losses are due to the high-intensity flux combined with limitations of the time resolution of the instrument. Since these losses will affect both the spectrum and the temporal distribution of the individual TGFs, results based on BATSE data need to be revisited, including our …
A new population of terrestrial gamma‐ray flashes in the RHESSI data
2015
Terrestrial gamma-ray flashes (TGFs) are the most energetic photon phenomenon occurring naturally on Earth. An outstanding question is as follows: Are these flashes just a rare exotic phenomenon or are they an intrinsic part of lightning discharges and therefore occurring more frequently than previously thought? All measurements of TGFs so far have been limited by the dynamic range and sensitivity of spaceborne instruments. In this paper we show that there is a new population of weak TGFs that has not been identified by search algorithms. We use the World Wide Lightning Location Network (WWLLN) to identify lightning that occurred in 2006 and 2012 within the 800 km field of view of Reuven Ra…
Enhanced detection of terrestrial gamma-ray flashes by AGILE
2015
Abstract At the end of March 2015 the onboard software configuration of the Astrorivelatore Gamma a Immagini Leggero (AGILE) satellite was modified in order to disable the veto signal of the anticoincidence shield for the minicalorimeter instrument. The motivation for such a change was the understanding that the dead time induced by the anticoincidence prevented the detection of a large fraction of Terrestrial Gamma‐Ray Flashes (TGFs). The configuration change was highly successful resulting in an increase of one order of magnitude in TGF detection rate. As expected, the largest fraction of the new events has short duration (<100 μs), and part of them has simultaneous association with light…
The Modular X- and Gamma-Ray Sensor (MXGS)of the ASIM Payload on the International Space Station
2019
The Modular X- and Gamma-ray Sensor (MXGS) is an imaging and spectral X- and Gamma-ray instrument mounted on the starboard side of the Columbus module on the International Space Station. Together with the Modular Multi-Spectral Imaging Assembly (MMIA) (Chanrion et al. this issue) MXGS constitutes the instruments of the Atmosphere-Space Interactions Monitor (ASIM) (Neubert et al. this issue). The main objectives of MXGS are to image and measure the spectrum of X- and γ-rays from lightning discharges, known as Terrestrial Gamma-ray Flashes (TGFs), and for MMIA to image and perform high speed photometry of Transient Luminous Events (TLEs) and lightning discharges. With these two instruments sp…
Constraining spectral models of a terrestrial gamma‐ray flash from a terrestrial electron beam observation by the Atmosphere‐Space Interactions Monit…
2021
Terrestrial Gamma ray Flashes (TGFs) are short flashes of high energy photons, produced by thunderstorms. When interacting with the atmosphere, they produce relativistic electrons and positrons, and a part gets bounded to geomagnetic field lines and travels large distances in space. This phenomenon is called a Terrestrial Electron Beam (TEB). The Atmosphere-Space Interactions Monitor (ASIM) mounted on-board the International Space Station detected a new TEB event on March 24, 2019, originating from the tropical cyclone Johanina. Using ASIM's low energy detector, the TEB energy spectrum is resolved down to 50 keV. We provide a method to constrain the TGF source spectrum based on the detected…
Production altitude and time delays of the terrestrial gamma flashes: Revisiting the Burst and Transient Source Experiment spectra
2008
[1] On the basis of the RHESSI results it has been suggested that terrestrial gamma flashes (TGFs) are produced at very low altitudes. On the other hand some of the Burst and Transient Source Experiment (BATSE) spectra show unabsorbed fluxes of X rays in the 25–50 keV energy range, indicating a higher production altitude. To investigate this, we have developed a Monte Carlo code for X-ray propagation through the atmosphere. The most important features seen in the modeled spectra are (1) a low-energy cutoff which moves to lower energies as TGFs are produced at higher altitudes, (2) a high-energy cutoff which moves to lower energies as TGFs are observed at larger zenith angles, and (3) time d…
A new method reveals more TGFs in the RHESSI data
2012
[1] This letter presents a new search algorithm for identifying Terrestrial Gamma ray Flashes (TGFs) in the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) data. The algorithm has been applied to data from the period 2004–2006 and we have found more than twice as many TGFs as previously reported. The new TGFs follow the same geographical and seasonal variations as the previously reported TGFs. The match percentage between the new TGFs and World Wide Lightning Location Network (WWLLN) data is comparable to the RHESSI catalog TGFs. Our results shows that previous searches only identified the most intense events, and that there might be a large population of faint TGFs.
A terrestrial gamma-ray flash and ionospheric ultraviolet emissions powered by lightning.
2020
Gamma-ray flash from a lightning leader Terrestrial gamma-ray flashes (TGFs) are millisecond pulses of gamma rays produced by thunderstorms. Neubert et al. observed a TGF from above, using instruments on the International Space Station. High-speed photometry in optical, ultraviolet, x-ray, and gamma-ray bands allowed them to determine the sequence of events that produced the TGF. Emission from an intracloud lightning leader was followed within a millisecond by the TGF. The subsequent lightning flash produced an electromagnetic pulse, which induced expanding waves of ultraviolet emission in the ionosphere above the thunderstorm, called an elve. The authors conclude that high electric fields …