A research flight into a thunderstorm has yielded evidence of a "rogue" form of antimatter, photons that don't match any known examples of antiparticles, researchers are reporting.
Positrons, the antimatter version of electrons, have been detected in powerful storms before, but University of New Hampshire scientist Joseph Dwyer says the antimatter he and his colleagues detected when their aircraft was in a thunderstorm on a research flight cannot be explained by any of the currently known processes for their creation.
That flight was in 2009, but the researchers are just now reporting their discovery in the Journal of Plasma Physics.
Their unexpected finding "was so strange that we sat on this observation for several years," says Dwyer.
The detection of a large cloud of positrons within the thunderstorm in the absence of other expected physical phenomena such as strong gamma-ray emissions is perplexing, and runs counter to the currently understood physics of antimatter, the researchers say.
It is understood that violent thunderstorms can create such sudden flashes of gamma rays - resulting in the production of pairs of electrons and their antimatter positron twins as the rays interact with the atmosphere - but there should be detectable gamma ray increase with any detection of positrons, the researchers point out.
That's not what was seen, Dwyer says.
"We should have seen bright gamma-ray emissions along with the positrons," he says. "But in our observations, we first saw a positron cloud, then another positron cloud about seven kilometers away and then we saw a bright gamma-ray glow afterwards. So it's all not making a whole lot of sense."
Dwyer and colleagues from Florida Tech and the University of California, Santa Cruz, made the observation while aboard an instrument-carrying Gulfstream V aircraft operated by the National Center for Atmospheric Research.
The discovery could be tied up with how thunderstorms build up charges that are then released as lightning, but since the observations don't fit with what's been understood to date about the process it's complicating the picture, Dwyer says.
"We really don't understand how lightning gets started very well because we don't understand the electrical environment of thunderstorms," he says.
As for the apparent "rogue" antimatter, it's a puzzle still awaiting a solution, he adds.
"We really have no good explanation for it."