Positrons observed to originate from thunderstorms

Abstract

Thunderstorms are the result of warm, moist air moving rapidly upward, then cooling and condensing. Electrification occurs within thunderstorms (as noted by Benjamin Franklin), produced primarily by frictional processes among ice particles. This leads to lightning discharges; the types, intensities, and rates of these discharges vary greatly among thunderstorms. Even though scientists have been studying lightning since Franklin's time, new phenomena associated with thunderstorms are still being discovered. In particular, a recent finding by Briggs et al. [2011], based on observations by the Gamma‐Ray Burst Monitor (GBM) instrument on NASA's satellite‐based Fermi Gamma‐ray Space Telescope (Fermi), shows that positrons are also generated by thunderstorms. Positrons are the antimatter form of electrons—they have the same mass and charge as an electron but are of positive rather than negative charge; hence the name positron. Observations of positrons from thunderstorms may lead to a new tool for understanding the electrification and high‐energy processes occurring within thunderstorms. New theories, along with new observational techniques, are rapidly evolving in this field.

The true fluence distribution of terrestrial gamma flashes at satellite altitude

“…In Figure 5b we keep the relative sensitivity fixed at X = 2.7 and let the daily TGF detection rate ( Y ) vary from 1 to 6. The daily TGF detection rate for RHESSI is fairly well established by Grefenstette et al [2009], while Fermi's daily detection rate is given as approximately 1 [ Fishman , 2011]. As described above, based on the information given by Briggs [2011, also personal communication, 2011] we found that the equivalent (to RHESSI) daily detection rate for Fermi after downloading data, due to sensitivity differences only, is 1.5 ± 0.3 TGFs/day, with 1.2 (1.8) TGFs/day corresponding to TGFs with higher (lower) fluence over ocean than land.…”

“…For the first 53 TGFs measured by Fermi they observed 0.03 TGFs/day when a 16 ms on‐board trigger window was applied to the NaI scintillators, which increased to 0.3 TGFs/day when the same window was applied to the BGO detectors [ Fishman et al , 2011]. However, after the Fermi team started downloading most of the data obtained over regions where TGFs are produced, Fishman [2011] reported that more than 1 TGF/day has been observed. According to Briggs [2011; M. Briggs, personal communication, 2011] their ground search found 234 TGFs in 591.8 hours of data over regions which are expected to have a high TGF rate.…”

Positron-impact electronic excitations and mass stopping power of H2

“…Such technologies require a detailed understanding of positron collision processes to improve their accuracy and reliability. Positron collisions with atoms and molecules can also help in resolving a number of fundamental problems such as unknown sources of positron jets in the center of our galaxy [3], the missing antimatter [4], spectroscopic and gravitational properties of antimatter [5,6] and very recent observations of positron clouds produced during thunderstorms [7].…”