Space Traffic Boosts Noctilucent Clouds

July 29, 2022: Never before have so many rockets been launched. In 2021, the space agencies of Earth broke the all-time record for global rocket launches with 133, and in 2022 it looks like the record will be broken again with more than 150. China and SpaceX are big contributors to this increase.

High above Earth, something else is increasing: Noctilucent clouds (NLCs). It’s no coincidence. A new paper just published in the AGU journal for Earth and Space Science confirms that “space traffic has a strong influence on the interannual variability of these bright mesospheric clouds.”

Above: Noctilucent clouds over Anchorage AK on July 26, 2022. Credit: Todd Salat.

Noctilucent clouds are a natural phenomenon. During summer months, wisps of water vapor rise up to the mesosphere, 83 km high, and crystalize around specks of disintegrated meteoroids. Sky watchers at northern latitudes can easily see the clouds, which are filled with fine ripples and shine at night with an electric blue color.

Rocket launches are boosting NLCs. A team of researchers led by Michael Stevens of the Naval Research Lab in Washington, DC, looked at data from NASA’s AIM spacecraft, which was launched in 2007 to study noctilucent clouds. They found a strong correlation between the number of rockets launched each July and the abundance of clouds in the mesosphere. 

Above: July rocket launches (black) vs. the abundance of noctilucent clouds (red)

The link is simple: Rockets produce plumes of water vapor. Winds carry these plumes toward the polar mesosphere where they become raw material for NLCs. Rockets launched in the “morning” between 11 pm and 10 am local time are most effective. During those times, diurnal wind patterns push the plumes toward the noctilucent zone.

Researchers have long known that rockets can produce NLCs. Seminal studies led by Stevens in the early 2000s linked specific space shuttle launches to outbursts of the clouds over both of Earth’s poles (refs: #1, #2). The shuttle program ended in 2011, but the “rocket effect” has continued and probably increased (researchers are still investigating the trends at mid-latitudes during the satellite era).

This is good news for sky watchers who love seeing “frosted meteor smoke” light up the night. Rockets make NLCs both brighter and more widespread. Researchers, on the other hand, may have mixed feelings. NLCs can be a sensitive indicator of changes to Earth’s climate system–e.g., revealing long-range teleconnections and the abundance of  greenhouse gases in the upper atmosphere. Rocket launches could swamp these delicate signals.

Either way, the launch schedule continues. Be alert for noctilucent clouds!

Cosmic Rays are Decreasing

July 26, 2022: Cosmic rays in the atmosphere are rapidly subsiding. In the past year alone, radiation levels in the air high above California have plummeted more than 15%, according to regular launches of cosmic ray balloons by and Earth to Sky Calculus. The latest measurement on July 23, 2022, registered a 6 year low:

This development, while sudden, is not unexpected. Cosmic rays from deep space are repelled by solar activity; when one goes up, the other goes down. Since 2021, Solar Cycle 25 has roared to life faster than forecasters expected. The onset of the new solar cycle has naturally led to a decrease in cosmic radiation reaching Earth.

To many readers this may sound counterintuitive. After all, don’t solar flares produce radiation? Yes, but most high-energy radiation doesn’t come from the sun; it comes from deep space. Every day galactic cosmic rays from distant supernova explosions pass through the Solar System. When they hit the top of Earth’s atmosphere, they create a secondary spray of radiation, which we measure using sensors onboard our balloons.

The sun makes it more difficult for these cosmic rays to reach Earth. Simply put, when the sun is active, its magnetic field gets stronger and more tangled. Cosmic rays have trouble penetrating the magnetic thicket. Also, individual CMEs sweep aside cosmic rays, causing sharp reductions called “Forbush Decreases.” The two effects blend together to bring daily radiation levels down.

Above: Earth to Sky students launch a cosmic ray balloon on July 23, 2022.

There is considerable interest in atmospheric cosmic rays. Climate scientists are engaged in a lively debate about whether or not cosmic rays affect cloud cover. (The consensus seems to be mostly not.) Cosmic rays also penetrate aircraft, boosting the risk of cancer among frequent fliers and flight crews.

Solar Maximum is expected in 2025, so the downward trend in cosmic radiation should continue for years to come. How low will it go? Stay tuned for updates.

Solar Tsunami and CME

July 21, 2022: Sunspot AR3060 exploded during the early hours of July 21st (0110 UT), producing a C5-class solar flare and a solar tsunami. The “tsunami” is the shadowy shock wave seen racing away from the blast site in this extreme ultraviolet movie from NASA’s Solar Dynamics Observatory:

Soon after the explosion, the US Air Force reported a Type II solar radio burst–a natural form of radio noise produced by shock waves in the leading edge of a CME. Characteristics of the burst suggested that a CME was tearing through the sun’s atmosphere at a speed of 1063 km/s (2.4 million mph).

Coronagraphs onboard the Solar and Heliospheric Observatory (SOHO) have since seen the CME:

In the movie we see a superposition of multiple CMEs. The brightest clouds at the 8 o’clock and 10 o’clock positions may be from farside eruptions. They are not heading for Earth. Of greater interest is a faint full-halo CME which emerges just before 0206 UT. That one was launched by the tsunami and is squarely inside the Earth strike zone. NOAA forecasters expect it to arrive on July 23rd, possibly sparking G2-class geomagnetic storms. Solar flare alerts: SMS Text.

The Bastille Day Event

July 14, 2022: You know a solar flare is strong when even the Voyager spacecraft feel it. Twenty-two years ago today (July 14, 2000) the sun exploded with so much force, it sent shockwaves to the edge of the solar system.

Earth was on the doorstep of the blast, nicknamed the “Bastille Day Event” because it happened on the national day of France. Subatomic particles accelerated by the flare peppered satellites and penetrated deep into Earth’s atmosphere. Radiation sensors on Earth’s surface registered a rare GLE–a “ground-level event.”

Above: SOHO images of the Bastille Day solar flare (left) and CME (right). The onset of snow in the images is a result of energetic protons hitting the spacecraft

“People flying in commercial jets at high latitudes would have received double their usual radiation dose,” says Clive Dyer of the University of Surrey Space Centre in Guildford UK, who studies extreme space weather. “It was quite an energetic event–one of the strongest of the past 20 years.”

A day later the CME arrived. Impact on July 15th sparked an extreme (Kp=9) geomagnetic storm. The sun had just set on the east coast of North America when the first auroras appeared.

“I was out in the yard doing chores and saw bright red auroras straight overhead,” recalls Uwe Heine of Caswell County, North Carolina. “I called over to our neighbor, Carrie, who was also outside. I told her those were not sunset colors. It was an aurora, and super rare to see this far south!”

Above: Auroras on July 15, 2000, photographed by (left) Grant Privett of Farnborough UK and (right) NASA’s IMAGE spacecraft.

In New York, the sky exploded with light, recalls Lou Michael Moure. “I was living on Long Island at the time. A family member came running into my room, begging me to come outside to see ‘the sky on fire.’ The sky truly looked as if it was ablaze. Hues of white and green eventually gave way to reds that blanketed the heavens from horizon to horizon.”

By the time the storm was over on July 16th, auroras had been sighted as far south as Texas, Florida and Mexico.

A few other storms of the Space Age have have been equally strong, but the Bastille Day Event is special to researchers. It was the first major solar storm after the launch of SOHO, the Solar and Heliospheric Observatory. Data from the revolutionary young satellite taught researchers a lot, very quickly, about the physics of extreme flares.

Above: A modern MHD computer simulation of the Bastille Day explosion. Credit: Tibor Török et al., The Astrophysical Journal, 856:75 (22pp), 2018 March 20.

Tibor Török of Predictive Science, Inc., is one of many researchers still studying the Bastille Event decades later. “The event took place close to disk center, so we had a great view of the action,” he says. Török recently applied a modern magnetohydrodynamic (MHD) computer model to some of the data, and found that 1033 ergs of magnetic energy were released in the explosion–about the same as a thousand billion WWII atomic bombs.

No wonder the Voyagers felt it.

It took the Bastille Day CME months to reach the distant spacecraft. Voyager 2 felt it 180 days later, Voyager 1 took 245 days. Being near the edge of the solar system, both spacecraft were naturally bathed in high levels of cosmic rays. The CME swept aside that ambient radiation, creating a temporary reduction called a “Forbush Decrease.” Conditions returned to normal 3 to 4 months later and, finally, the storm was over.

Could another Bastille Day Event be in the offing? Solar Cycle 25 is ramping up, with a new Solar Max expected in 2025. Stay tuned.

more aurora photos: from Ronnie Sherrill of Troutman, North Carolina

Starfish Prime: The First Accidental Geomagnetic Storm

July 9, 2022: Sixty years ago today, one of the biggest geomagnetic storms of the Space Age struck Earth. It didn’t come from the sun.

“We made it ourselves,” recalls Clive Dyer of the University of Surrey Space Centre in Guildford UK. “It was the first anthropogenic space weather event.”

On July 9, 1962, the US military detonated a thermonuclear warhead 250 miles above the Pacific Ocean–a test called “Starfish Prime.” What happened next surprised everyone. Witnesses from Hawaii to New Zealand reported auroras overhead, magnificent midnight “rainbow stripes” that tropical sky watchers had never seen before. Radios fell silent, then suddenly became noisy as streetlights went dark in Honolulu.

Above: ‘Nuclear auroras’ viewed from Honolulu (left) and from a surveillance aircraft (right) on July 9, 1962.

Essentially, Starfish Prime created an artificial solar storm complete with auroras, geomagnetic activity, and blackouts. Much of the chaos that night was caused by the electromagnetic pulse (EMP)–a ferocious burst of radiation that ionized the upper atmosphere. Ionized air over the Pacific pinned down Earth’s magnetic field, then let it go again when the ionization subsided. The rebound created a manmade geomagnetic storm for hundreds of miles around the blast zone.

Dyer, who is widely known for his studies of extreme space weather events, was still in school when the bomb exploded. “In 1962 the Cold War was red hot, and we all thought the end was nigh,” he says. “Starfish Prime was a defining event.”

“The explosion led to the early demise of all the spacecraft in orbit at the time. These included Ariel-1, the UK’s first spacecraft, and Telstar-1, a US communications satellite which had the bad luck to be launched the very next day.”

Credit: R.E. Fischell, “ANNA-1B Solar Cell Damage Experiment,” Transcript of the Photovoltaic Specialists Conference, April 10, 1963, Washington DC.

Normally, geomagnetic storms bring down satellites via orbital decay. The upper atmosphere heats up and expands to the point where it can pull satellites down toward Earth. Starfish Prime was different.

“The explosion filled Earth’s magnetosphere with energetic electrons,” explains Dyer. “Electrons were injected by the gradual beta decay of fission products and added to our planet’s natural radiation belts. There were increased fluxes of trapped electrons for many years after the blast.”

These artificial electrons hit satellites hard, degrading their electronics and solar arrays.

“Ariel-1 became almost unusable after 4 days due to power degradation and tape recorder failure,” recalls Dyer. “The Telstar satellite lasted until November 1962 when its command decoder failed. It still managed to provide the first transatlantic TV feed, synchronize UK/US time to 1 microsecond and inspired the Tornado’s rock classic ‘Telstar,’ which used recordings of a flushing toilet played backwards.”

Starfish Prime serves as a warning of what could happen if Earth is blasted by high doses of radiation. Sixty years later, researchers are still learning what it can teach us about the vulnerability of power grids. An even scarier atmospheric explosion may have been Soviet test 184 (also designated K3) on October 22, 1962, which set fires and knocked out hundreds of miles of power lines in Kazakhstan. That, however, is a different anniversary.

A Sudden Increase in Noctilucent Clouds

July 1, 2022: Something unexpected just happened in the mesosphere. As June came to an end, NASA’s AIM spacecraft detected a sharp increase in the frequency of noctilucent clouds (NLCs), the most in 15 years:

“In the last couple of days we saw a huge spike in the clouds,” says Cora Randall, a professor at the University of Colorado Boulder. Randall works with AIM data and she prepared the plot, above.

NLCs are Earth’s highest clouds. Seeded by meteoroids, they float at the edge of space more than 80 km above the ground. NLCs form when summertime wisps of water vapor rise up to the mesosphere, allowing water to crystallize around specks of meteor smoke.

Oliver Schwenn witnessed the outbreak on June 30th from Aarhus, Denmark:

“I photographed the display shortly before midnight,” says Schwenn. “The clouds were shining brightly in the night sky.”

What’s causing this? It could be SpaceX.

“We’re speculating that the spike might be due to extra water vapor transported to higher latitudes from rocket launches,” says Randall. “But much more quantitative analysis would be required to confirm that or not.”

The timing makes sense. It takes about 10 days for water vapor from rocket engines to waft up to the mesosphere. This takes us back to SpaceX’s launch of the Globalstar satellite on June 19th, which caused a number of remarkable phenomena in the sky due to the extra burn time of its second-stage engine. Noctilucent clouds may be yet another by-product of that unusual launch.

Noctilucent clouds are normally a polar phenomenon. However, since the outburst began we have received reports of NLCs from as far south as Washington State and Oregon. Look for the clouds, ripply and electric-blue, just after sunset.

Strange Things in the Sky, Courtesy of SpaceX

June 20, 2022: On Sunday morning, June 19th, SpaceX launched a Falcon 9 rocket from Cape Canaveral (0427 UT) carrying a Globalstar communications satellite. Within hours, people around the world started seeing strange things in the sky. First came the “smoke ring.” Jerrod Wood video recorded it from central Illinois:

“I believe it shows the orbital insertion of the Globalstar FM15 satellite,” says Wood.

He’s right. Almost two hours after launch, the upper stage of the Falcon 9 rocket deployed the Globalstar satellite; the smoke ring Wood saw was the “puff” of separation. At the time, the rocket was more than 1100 km high, so people were able to see it across much of North America. Check out these images: from Arizona, Missouri, Iowa and California.

An hour after the smoke ring, things got really strange. Sky watchers in New Zealand saw this:

“It looked like a beautiful galaxy,” says photographer Alasdair Burns of Twinkle Dark Sky Tours on Stewart Island. “It was a very slowly rotating spiral that started small and gradually expanded. Eventually it became so large and faint that it could no longer be seen. There were a group of us on our balcony watching it and none of us had ever seen anything like it.”

This spiral was caused by the Falcon 9’s upper stage venting leftover fuel just before deorbiting into the Pacific Ocean. The upper stage was probably spinning on its longest axis to stabilize flight orientation–hence the spiral shape. Similar spirals have been seen after previous Falcon 9 launches.

Finally, David Cortner of Rutherford College, North Carolina, saw something truly head-scratching. He calls it a “rocket powered aurora.” This 8-frame mosaic shows a red band that appeared approximately 11 minutes after the Falcon 9’s liftoff from Cape Canaveral:

“I went out to watch the midnight launch,” says Cortner. “Here in western North Carolina, I was hoping for a faint, moonlit ‘jellyfish’–the kind of display we see after many SpaceX launches.” But that’s not what happened.

“The rocket’s trajectory was much higher than I expected,” he continues. “It was almost 500 km high by the time it was due east of me, not 150-200 km like most SpaceX flights up the Atlantic coast. As a result, the rocket passed by unseen.”

“Instead, I noticed this red glow spreading along the flight path a minute or two after the rocket’s closest approach,” he says. “It looked like the aurora borealis.”

Could it have been auroras? Probably not. Low-latitude red auroras typically appear only during strong geomagnetic storms. At the time of the photo, however, global geomagnetic activity was low (Kp=3); there was no space weather event in progress.

SPACEX MYSTERY, SOLVED: The mystery of SpaceX’s “rocket powered auroras” has been solved. On Sunday morning, June 19th, SpaceX launched a Falcon 9 rocket from Cape Canaveral. Photographers accustomed to seeing these launches were surprised when something unusual appeared. A red glow stretched across the Milky Way. It looked like the aurora borealis, as shown in this photo from Christopher Hoffman in Saint Mary’s County, Maryland:

“I went out with some first time photographers to teach them how to set up their cameras for night sky photography,” says Hoffman. “We took a 30 second exposure, and when the exposure was finished I saw this red glowing area covering the Milky Way.”

Photographers in New York, Ohio, North Carolina and Tennessee saw it, too. The glow appeared about 10 minutes after the Falcon 9 rocket lifted off, and many observers likened its appearance to auroras. However, there was no geomagnetic storm in progress. It had to be the rocket.

What happened? Space physicist Jeff Baumgardner of Boston University has the answer: “This glow is probably the exhaust gasses from the rocket’s 2nd stage causing the ionosphere to recombine quickly. This is a well studied phenomenon when rocket engines are firing in the altitude regime 200-250 km.”

Above: A similar display of red light appeared over the eastern USA following the launch of a Titan IV rocket on April 30, 2005. [full story]

In simplified form, here is what happens: The upper atmosphere is filled with oxygen ions (O+). Of particular interest is the F-layer of the ionosphere, because it is rich in O+. When the Falcon 9 rocket reaches the F-layer, it adds water (H2O) and carbon dioxide (CO2) to the mix, spewing the molecules out of its engine. Oxygen ions are hungry for electrons, and the newly arriving molecules are eager to provide them. Electrons “re-combine” with oxygen, turning ions into atoms. As electrons cascade down the oxygen atom’s energy levels, they emit red photons at a wavelength of 6300 Å–the same color as red auroras.

more images: from Josh Thum of Sevierville, Tennessee; from Brenda Calinawan of Kortright, New York; from David Cortner of Rutherford College, NC