Lightning flashes conducive to the production and escape of gamma radiation to space

Abstract

[1] Gamma radiation observed in space has been associated with lightning flashes in thunderstorms. These special flashes do not appear to be the large and energetic positive ground flashes that also produce sprites. Considerations of gamma ray attenuation in air indicate that such flashes may not produce gamma radiation at sufficient altitude to enable their escape to space. High-altitude intracloud lightning, most prevalent in the tropics where the tropopause is also high, may be a necessary source.Citation: Williams, E., et al. (2006), Lightning flashes conducive to the production and escape of gamma radiation to space,

Localization of the source of terrestrial neutron bursts detected in thunderstorm atmosphere

“…It is pertinent to note that the characteristics of the terrestrial g ray flashes detected in the near space aboard CGRO [Fishman et al, Table 1. Number, Flux Density, and Fluence of Neutrons at the "Detector Altitude" for Neutron Source Located at "Cloud Altitude" 1994] and RHESSI are explained more or less adequately by bremsstruhlung of ascending relativistic electron avalanches (for instance, [Dwyer and Smith, 2005;Dwyer, 2008;Cummer et al, 2005;Williams et al, 2006;Babich et al, 2007b;2008a, 2008b, 2008c), as in the earlier works, where the CGRO data were analyzed [e.g., Taranenko and Roussel-Dupre, 1996;Roussel-Dupre et al, 1998;Lehtinen et al, 1996Lehtinen et al, , 1999Lehtinen et al, , 2001Gurevich and Zybin, 2001;Babich et al, 2001Babich et al, , 2004b.…”

Origin and context of C. T. R. Wilson's ideas on electron runaway in thunderclouds

“…[53] Today, with the recent evidence (see Appendix B, note 20) that lightning can produce X-radiation at relatively close range [Moore et al, 2001;Dwyer et al, 2005], and can launch g radiation into space [Smith et al, 2005;Stanley et al, 2006;Williams et al, 2006], the coincidence results noted by Schonland and Viljoen [1933] seem plausible, but the long range paths for b rays outside the cloud where the electric field magnitude is often modest (tens of kV/m or less), are probably unrealistic. Nevertheless, Wilson's scenario for annihilating the (b ray-retarding) cloud top field by a lightning flash, to enable sustained propagation away from the cloud, may have an interesting parallel accounting for g radiation observed by the RHESSI satellite in space.…”

“…Today it is known that energetic gamma radiation is produced in abundance by thunderclouds [Parks et al, 1981;Parks, 1985, 1992;Eack et al, 1996aEack et al, , 1996bEack et al, 2000;Moore et al, 2001;Dwyer et al, 2004aDwyer et al, , 2004bDwyer et al, , 2005Smith et al, 2005], contrary to Wilson's expectation. It is also recognized that the substantially greater ranges in air of gamma rays (in comparison with b rays of the same energy) are needed for energetic particles to escape the dense atmosphere to be detected in space [Williams et al, 2006]. Wilson may have underestimated this g contribution because he did not envisage, at least initially, the electron avalanche process which will greatly multiply the numbers of energetic electrons from bremsstrahlung.…”

“…The essentially negative results of Schonland [1930] in his initial search beneath the cloud undoubtedly played a role here. Evidence has accumulated in recent years for a process of electron runaway and gamma ray production associated with lightning in the upper portion of thunderclouds [Smith et al, 2005;Stanley et al, 2006;Williams et al, 2006], but the details of this process needed for comparisons with Wilson's speculations in 1956 remain to be disclosed.…”

Electromagnetic radiation of simulated mid-gap streamers

“…On the other hand, not long ago was discover that lightning can be the source of the Terrestrial Gamma ray Flashes [1] and especially its leader processes [2]. At ground, x-ray emissions are associated at the leader step phase [3][4][5].…”