A new paper, published in the Journal of Geophysical Research: Atmospheres, has quite the title. Obviously you shouldn’t judge a book by its cover, but we’d argue this one warrants close attention: “A terrestrial gamma-ray flash inside the eyewall of Hurricane Patricia.”
In layman terms, this means that one of the windiest hurricanes on record produced a fair bit of lightning, and at least one of those flashes was energetic enough to produce a beam of antimatter, which shot down to Earth. If you don’t think that’s cool, then that’s fine, but you’d be wrong.
Back in 2015, when Hurricane Patricia was wreaking havoc on Mexico’s west coast, records were being set. The intensity of this cyclonic creation was unparalleled, and scientists wanted to get a closer look. Thankfully, the National Oceanic and Atmospheric Administration (NOAA) have some specially designed planes that can fly into the hearts of hurricanes unharmed.
Sending one of their Hurricane Hunter planes into Patricia’s peak paroxysmal rage, they headed for the eyewall, a circumference of colossal thunderstorms, high winds and extreme weather. An instrument aboard the craft named ADELE, designed by engineers at the University of California Santa Cruz, picked up 184 counts of ionizing radiation in the blink of an eye – consistent with a lightning flash.
Based on the associated radio signal, and comparing the gamma-ray energy spectrum to simulations, the team concluded that ADELE – the Airborne Detector for Energetic Lightning Emissions – had happened upon a beam of positrons.
Positrons are the antimatter equivalents to electrons; they have the same mass, but an equal yet opposite charge. So what’s the alchemy behind this spectacular occurrence of lightning-generated antimatter?
The average lightning bolt involves the transfer of a billion or so joules of energy. As it happens, a 2017 study doubled-down on the notion that lightning of any sort, thanks to their high-energy nature, are natural particle accelerators.
Bolts create a rapid cascade of electrons that were suspected to be colliding with atmospheric molecules and producing nuclear reactions in the sky. These reactions were thought to be producing high-energy gamma rays too, along with neutrinos, neutrons and positrons.
Models indicated that, during some lightning flashes, it was expected that a beam of electrons would shoot into space just as oppositely charged (and therefore repelled) positrons moved downwards, producing what is known as a terrestrial gamma-ray flash (TGF).
TGFs have been detected by space-based instrumentation for several decades now, but the satellites up there were only seeing one half of the phenomenon.
Fortunately, the event detected by NOAA in 2015 has been found to match the models perfectly: ADELE picked up a downward blasted beam of positrons, a component of an upward-propagating radiation flare shooting off into space.
Detecting this TGF-linked antimatter beam wasn’t a surprise, but it is, however, the first time it’s been observed, which is clearly marvelous. If you’re wondering: no, you’d have to be right near the source of this beam for it to be of any danger.
This certainly won’t be the last time an antimatter beam like this will be detected. You might not even need to brave flying into hurricanes; the team’s study explains that “this reverse gamma‐ray beam penetrates to low enough altitudes to allow ground‐based detection of typical upward TGFs from mountain observatories.”
Not quite as cool as flying into a hurricane, though.