Studying the time histogram of a terrestrial electron beam detected from the opposite hemisphere of its associated TGF. Issue 5 (12th May 2016) - Sarria, D.
Abstract: Terrestrial gamma‐ray flashes are bursts of X/gamma photons, correlated to thunderstorms. By interacting with the atmosphere, the photons produce a substantial number of electrons and positrons. Some of these reach a sufficiently high altitude that their interactions with the atmosphere become negligible, and they are then guided by geomagnetic field lines, forming a Terrestrial Electron Beam. On 9 December 2009, the Gamma‐Ray Burst Monitor (GBM) instrument on board the Fermi Space Telescope made a particularly interesting measurement of such an event. To study this type of event in detail, we perform Monte‐Carlo simulations and focus on the resulting time histograms. In agreement with previous work, we show that the histogram measured by Fermi GBM is reproducible from a simulation. We then show that the time histogram resulting from this simulation is only weakly dependent on the production altitude, duration, beaming angle, and spectral shape of the associated terrestrial gamma‐ray flash. Finally, we show that the time histogram can be decomposed into three populations of leptons, coming from the opposite hemisphere, and mirroring back to the satellite with or without interacting with the atmosphere, and that these populations can be clearly distinguished by their pitch angles. Key Points: Fermi 091214 event time histogram accurately reproduced The synthetic time histogram is reproducible by a wide range of possible TGFs The lepton time histogram can be split into three populations by looking at the pitch angles