Sept. 24, 2021: Lightning on Earth is getting weirder and weirder. On the evening of Sept. 20th, Puerto Rican photographer Frankie Lucena pointed his Sony A7s camera at an offshore electrical storm. This is what he saw:
“This Gigantic Jet plasma event occurred over a very powerful thunderstorm near the Virgin Islands just ahead of Tropical Storm Peter,” says Lucena. “I can’t believe I was able to capture such amazing details.”
Indeed, this is one of the best-ever photos of a Gigantic Jet. Sometimes called “Earth’s tallest lightning,” because they reach the ionosphere more than 50 miles high, the towering forms were discovered near Taiwan and Puerto Rico in 2001-2002. Since then, only dozens of Gigantic Jets have been photographed. They seem to love storms over water and are famous for surprising passengers onboard commercial aircraft.
In 2017 and 2018, lightning researcher Oscar van der Velde of the Universitat Politècnica de Catalunya set up high speed cameras on the northern coast of Colombia in a dedicated campaign to capture Gigantic Jets. In three months of observing time he managed to capture only 12. That’s how elusive they are.
Above: The red arrow points from Lucena’s camera to the offshore electrical storm.
“Frankie has photographed a rare Gigantic Jet with ‘carrot’ morphology, first reported by Su et al (2003),” notes van der Velde. “The other, more common type of jet has a ‘tree’ morphology.” Here is a comparison: trees vs. carrots.
“Carrot jets” are remarkable for their internal beads–that is, bright balls of light hundreds of meters wide. Lucena caught dozens of them illuminating the jet’s midsection. They might be places where streamers inside the jet are intersecting, or regions of enhanced heating.
“We don’t know,” says van der Velde. “Gigantic Jets are not easily placed in front of a spectrograph.”
Meanwhile, Lucena is still marveling at what happened. “This is the brightest Gigantic Jet I have ever seen. It was truly remarkable.”
Sept. 24, 2021: No solar storms? No problem. Earth has learned to make its own auroras. New results from NASA’s THEMIS-ARTEMIS spacecraft show that a type of Northern Lights called “diffuse auroras” comes from our own planet–no solar storms required.
Diffuse auroras look a bit like pea soup. They spread across the sky in a dim green haze, sometimes rippling as if stirred by a spoon. They’re not as flamboyant as auroras caused by solar storms. Nevertheless, they are important because they represent a whopping 75% of the energy input into Earth’s upper atmosphere at night. Researchers have been struggling to understand them for decades.
Above: Diffuse auroras and the Big Dipper, photographed by Emmanuel V. Masongsong in Fairbanks, AK
“We believe we have found the source of these auroras,” says UCLA space physicist Xu Zhang, lead author of papers reporting the results in the Journal of Geophysical Research: Space Physics and Physics of Plasmas.
It is Earth itself.
Earth performs this trick using electron beams. High above our planet’s poles, beams of negatively-charged particles shoot upward into space, accelerated by electric fields in Earth’s magnetosphere. Sounding rockets and satellites discovered the beams decades ago. It turns out, they can power the diffuse auroras.
The video, below, shows how it works. The beams travel in great arcs through the space near Earth. As they go, they excite ripples in the magnetosphere called Electron Cyclotron Harmonic (ECH) waves. Turn up the volume and listen to the waves recorded by THEMIS-ARTEMIS:
Above: A great electrical circuit in space powering diffuse auroras. ECH waves were sonified by NASA’s HARP (Heliophysics Audified: Resonances in Plasmas) software.
ECH waves, in turn, knock other electrons out of their orbits, forcing them to fall back down onto the atmosphere. This rain of secondary electrons powers the diffuse auroras.
“This is exciting,” says UCLA professor Vassilis Angelopoulos, a co-author of the papers and lead of the THEMIS-ARTEMIS mission. “We have found a totally new way that particle energy can be transferred from Earth’s own atmosphere out to the magnetosphere and back again, creating a giant feedback loop in space.”
According to Angelopoulos, Earth’s polar electron beams1 sometimes weaken but they never completely go away2, not even during periods of low solar activity. This means Earth can make auroras without solar storms.
The sun is currently experiencing periods of quiet as young Solar Cycle 25 sputters to life. Pea soup, anyone?
End Notes:
(1) Why do these electron beams exist? Earth’s magnetosphere is buzzing with energetic particles. Many of them are captured from the solar wind. When these particles strike the top of Earth’s atmosphere (the ionosphere), they dislodge electrons. Electric fields, which form naturally in Earth’s spinning magnetosphere, grab the liberated electrons and accelerate them skyward in collimated beams.
(2) Why don’t the beams ever go away? Short answer: Because the solar wind never stops blowing. Even when the sun is quiet, Earth’s magnetosphere is jostled and energized by the ever-present solar wind. As a result, electrons are always being knocked off the top of Earth’s atmosphere as described in Note #1. Although solar storms are not required for this process, solar storms can help. For instance, when a CME strikes Earth’s magnetosphere, the contents of the magnetosphere become extra-energized. Lots of particles furiously strike the top of Earth’s atmosphere, liberating even more electrons than usual. Earth’s electron beams can thus become super-charged. When the storm subsides, the electron beams may weaken, but they never vanish because even the quiet sun produces solar wind.
Zhang, X., Angelopoulos, V., Artemyev, A. V., Zhang, X.‐J., Liu, J. (2021). Beam‐driven electron cyclotron harmonic waves in Earth’s magnetotail. Journal of Geophysical Research: Space Physics, 126, e2020JA028743. https://doi.org/10.1029/2020JA028743s
Sept. 16, 2021: SpaceX just made history again. On Sept. 15th, a Falcon 9 rocket blasted off from Cape Canaveral carrying the first all-civilian crew to Earth orbit. “It was spectacular,” reports Bill Williams of Titusville, Florida. “Shooting from the west side of the Indian River, I recorded exhaust plumes and a dramatic ‘rocket nebula’ in the moonlit dusk skies.”
“I would rather have been on the rocket,” says Williams, “but the view from Earth wasn’t bad either!”
This mission, named “Inspiration4,” is setting a number of milestones. First of all, there are no astronauts onboard. It’s the first orbital spaceflight crewed entirely by private citizens. One of them, Hayley Arceneaux, age 29, is the youngest American ever to go to space. All 4 citizens received astronaut training from SpaceX, including orbital mechanics, microgravity exercises and mission simulations.
Arceneaux is also a pediatric cancer survivor, and the flight is raising money for childhood cancer research. The seat next to her on the spacecraft was raffled off, raising $200 million for the St. Jude Children’s Research Hospital, where Arceneaux’s life was saved years ago.
Above: The crew capsule with its bubble-shaped window
To top it all off, the crew are orbiting higher than any astronauts since STS-125 in 2009. They’re actually above the International Space Station.
If all goes as planned, the capsule will be in Earth orbit until Sept. 19th. One end of the spacecraft has a bubble-shaped window, giving the space travelers an unparalleled view of Earth. Here on the ground, we can look up and see them, too. The capsule is about as bright as a 3rd magnitude star, easy to spot from rural areas. For local flyby predictions, check Heavens Above.
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