By Stephen Beech via SWNS
Most tropical lightning storms are RADIOACTIVE, reveals new research.
Observations from a retrofitted U2 American spy plane found a “surprising” amount and variety of gamma radiation is produced in large tropical thunderstorms.
In the 1990s, NASA satellites built to spot high-energy particles coming from supernovas and other star-sized objects discovered a surprise — high energy gamma radiation bursts coming from Earth.
While it didn’t take long for researchers to work out that the radioactive supercharged particles were coming from thunderstorms, how commonly the phenomenon happened remained a mystery.
Satellites weren’t built to find gamma radiation coming from Earth, and they had to be in just the right place at just the right time to do so.
Now, after years of making do with platforms not ideal for the task, a team of scientists secured a chance to fly a retrofitted U2 spy plane owned by NASA over storms to take a proper look.
The team describe in two new papers, published in the journal Nature, how gamma radiation produced in thunderstorms is “far more common” than anyone thought.
Co-author Dr. Steve Cummer, of Duke University, North Carolina, said: “There is way more going on in thunderstorms than we ever imagined.
NASA satellites“As it turns out, essentially all big thunderstorms generate gamma rays all day long in many different forms.”
He explained that the general physics behind how thunderstorms create high-energy flashes of gamma radiation is not a mystery.
As thunderstorms develop, swirling drafts drive water droplets, hail and ice into a mixture that creates an electric charge much like rubbing a balloon on a shirt.
Positively charged particles end up at the top of the storm while negatively charged particles drop to the bottom, creating an “enormous” electric field that can be as strong as 100 million AA batteries stacked end-to-end.
When other charged particles – such as electrons – find themselves in such a strong field, they accelerate.
Dr. Cummer says that if they accelerate to high enough speeds and happen to strike an air molecule, they knock off more high-energy electrons.
The process cascades until the collisions have enough energy to create nuclear reactions, producing “extremely strong and extremely fast” flashes of gamma rays, antimatter and other forms of radiation.
Aircraft flying close to thunderstorms have also seen a faint glow of gamma radiation coming from clouds.
These storms seem to have enough energy to produce a low-level simmering of gamma radiation, but something prevents it from creating an explosive burst like a popping corn kernel.
Dr. Cummer said: “A few aircraft campaigns tried to figure out if these phenomena were common or not, but there were mixed results, and several campaigns over the United States didn’t find any gamma radiation at all.
“This project was designed to address these questions once and for all.”
The team secured the use of a NASA ER-2 High-Altitude Airborne Science Aircraft. It flies over twice as high as commercial aircraft and about three miles above most thunderstorms.
It’s also extremely fast, giving the researchers chance to pick the exact thunderstorms they thought were most likely to produce results.
Project lead investigator Nikolai Østgaard, of the University of Bergen, Norway, said: “The ER-2 aircraft would be the ultimate observing platform for gamma-rays from thunderclouds.
“Flying at 20 km [12.4 miles], we can fly directly over the cloud top, as close as possible to the gamma-ray source.”
The researchers figured that if the phenomena were rare, then they’d barely see any at all.
But if they were common, then they’d see a lot.
And they saw a lot.
Over the course of a month, the ER-2 flew 10 flights over large storms in the tropics south of Florida, and nine of them yielded observations of the simmer of gamma radiation, which was also more dynamic than expected.
Dr. Martino Marisaldi, also of the University of Bergen, said: “The dynamics of gamma-glowing thunderclouds starkly contradicts the former quasi-stationary picture of glows, and rather resembles that of a huge gamma-glowing boiling pot both in pattern and behaviour.”
Given the size of a typical thunderstorm in the tropics, which get much larger than storms at other latitudes, the findings suggest that more than half of all thunderstorms in the tropics are radioactive.
The researchers believe that the low-level production of gamma radiation acts like steam boiling off a pot of water and limits how much energy can be built up inside.
The team were equally excited to see numerous examples of short duration and intense gamma radiation bursts coming from the same thunderstorms.
They almost always occurred in conjunction with an active lightning discharge.
The team say that suggests that the large electric field created by lightning is likely “supercharging” the already high-energy electrons, enabling them to create high-energy nuclear reactions.
There were also at least two other types of short gamma radiation bursts that had never been seen before.
One type is incredibly short – less than a thousandth of a second, while the other is a sequence of about 10 individual bursts that repeat over the course of around a tenth of a second.
Dr. Cummer said: “Those two new forms of gamma radiation are what I find most interesting.
“They don’t seem to be associated with developing lightning flashes.
“They emerge spontaneously somehow.
“There are hints in the data that they may actually be linked to the processes that initiate lightning flashes, which are still a mystery to scientists.”
Dr. Cummer says the amount of radiation being produced would only be dangerous if a person or object were quite close to the origination source.
He added: “The radiation would be the least of your problems if you found yourself there.
“Airplanes avoid flying in active thunderstorm cores due to the extreme turbulence and winds.
“Even knowing what we now know, I don’t worry about flying any more than I used to.”
