The rarity of terrestrial gamma-ray flashes: 2. RHESSI stacking analysis

摘要: Author(s): Smith, DM; Buzbee, P; Kelley, NA; Infanger, A; Holzworth, RH; Dwyer, JR | Abstract: We searched for gamma-ray emission from lightning using the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) satellite by identifying times when RHESSI was near over 2 million discharges localized Worldwide Lightning Location Network (WWLLN). then stacked together arrival relative to sferic times, correcting light propagation time satellite. The resulting profile is sensitive an average level of per discharge far lower than what can be recognized above background a single terrestrial flash (TGF). summed signal presumed small, previously unknown TGFs simultaneous with WWLLN remarkably weak: region 0 300 km beneath RHESSI’s footprint, (6.2±3.8)×10 detector counts/discharge are measured, as opposed typical range 12-50 counts identified solely signal. Under assumption broken power law differential distribution TGF intensities, we find that index must harden dramatically or cut off just below sensitivity limit current satellites and most scenarios less 1% produce belongs anywhere in same those observable. For minority where more few percent flashes TGF, these “TGFs” 10 luminosity faintest therefore closer stepped leaders. rarity holds not only observed but also any within ms sferic, allowing (for example) possibility different events upward negative leader positive intracloud triggered WWLLN’s detection. -3 -4