20 Years Ago, A Severe Geomagnetic Storm

Oct. 21, 2021: Paolo Bardelli will never forget Oct. 21, 2001. “The sky over my hometown in Italy suddenly filled with intense red auroras,” he recalls. “This happened exactly 20 years ago today.”

Above: Red auroras over Tradate, Italy (latitude +45N), on Oct. 21, 2001. Photo credit: Cesare Guaita

A trip down memory lane: In 2001, Solar Cycle 23 was peaking and solar activity was very high. Strong flares were a daily occurance. On Oct. 19th, giant sunspot AR9661 erupted twice in quick succession, producing almost identical X1.6-class solar flares. The double blast hurled two bright CMEs toward Earth: CME #1, CME #2.

This is what the sun looked like that day:

The first CME took only two days to reach Earth. It was fast and potent. The storm cloud’s arrival on Oct. 21, 2001, ignited a severe geomagnetic storm (Kp=8). Solar wind speeds in the CME’s wake topped 700 km/s, keeping the storm going for more than 15 hours.

In Troutman, North Carolina, Ronnie Sherril witnessed the CME’s impact. “Auroras were visible in twilight even before the evening sky faded to black,” says Sherril, who took this picture at 7:30 pm local time:

“By 10:30 pm the sky had exploded into bright red with yellowish beams,” says Sherril. “What an awesome display!”

Less than a day later the second CME arrived, and it happened all over again. Another 15 hours of strong-to-severe storming ensued. Using data from a global network of magnetometers, NOAA made this record of planetary K-indices during the two-day event:

Red auroras were sighted in Germany, France, Italy, Spain, Australia, Japan, and in the United States as far south as latitude 35N. Remarkably, there were no widespread power outages or satellite disruptions. The Internet functioned normally throughout. It was mainly an aurora show.

Some observers are ready for more. “We are hoping for something similar for Solar Cycle 25, as the sun has recently had a good increase in its activity,” says Bardelli. Indeed, young Solar Cycle 25 is intensifying, but Solar Max isn’t expected for another 3 to 4 years. Until then, browse the October 2001 Aurora Photo Gallery.

A Volcanic Comet Blows its Top

Oct. 14, 2021: So you think you know what a comet is? Think again. Comet 29P/Schwassmann-Wachmann is challenging old ideas. Astronomers call it a comet, but, really, “giant space volcano” might be a better description. It’s a 60-km-wide ball of ice orbiting the Sun beyond Jupiter, and it appears to be one of the most volcanically active bodies in the entire Solar System.

Comet 29P just blew its top … again. In late September 2021, 29P erupted 4 times in quick succession, blowing shells of “cryomagma” into space. Arizona amateur astronomer Eliot Herman has been monitoring the debris:

“Initially it looked like a bright compact object,” says Herman. “Now the expanding cloud is 1.3 arcminutes wide (bigger than Jupiter) and sufficiently transparent for background stars to shine through.”

When this object was discovered in 1927, astronomers thought they had found a fairly run-of-the-mill comet, unusual mainly because it was trapped in a nearly circular orbit between Jupiter and Saturn. 29P quickly proved them wrong as it began to erupt over and over again. Modern observations show that outbursts are happening as often as 20 times a year (almost 3 times the rate of the widely-quoted Wikipedia figure, 7.3 times per year).

“The current outburst, which began on Sept. 25th, appears to be the most energetic of the past 40 years,” says Dr. Richard Miles of the British Astronomical Association (BAA). “Within a span of only 56 hours, four eruptions took place in quick succession, creating a ‘superoutburst.'”

Miles is a leading researcher of 29P, and he has developed a theory to explain what’s happening. The “comet,” he believes, is festooned with ice volcanoes. There is no lava. The “magma” is a cold mixture of liquid hydrocarbons (e.g., CH4, C2H4, C2H6 and C3H8) akin to those found in the lakes and streams of Saturn’s moon Titan. In Miles’s model, the cryomagma contains a sprinkling of dust and it is suffused with dissolved gases N2 and CO, all trapped beneath a surface which, in some places, has the consistency of wax. These bottled-up volatiles love to explode when a fissure is opened–hence some of 29P’s more spectacular eruptions.

Above: A time series of previous outbursts from June 2020 – April 2021. These are all small compared to the current superoutburst. Source: Mission 29P.

In a seminal paper published 5 years ago, Miles studied the modern record of eruptions and he found some patterns. Data suggest that 29P rotates every 57.7 days. The most active vents are concentrated on one side of the ice-ball in a range of longitudes less than 150 degrees wide. At least 6 discrete sources have been identified.

While most outbursts fade within a week or so, this superoutburst is still visible. The rat-a-tat-tat eruption in September boosted the comet’s brightness 250-fold, and it hasn’t declined much since then. With an integrated magnitude between +10 and +11, the expanding cloud is well within the range of backyard telescopes.

“Comet 29P can be seen with an 8 inch ‘scope,” says Herman. “In smaller instruments it will appear to be a bright dot. To resolve the cloud and photograph individual stars shining through it, I used the big half-meter iTelescope T11.”

Ready see something weird? 29P is located in the constellation Auriga, easy to find high in the sky at midnight. Visit Sky&Telescope for observing tips. Also, for the latest news check out the BAA’s MISSION 29P website.

Auroras in the USA

Oct. 12. 2021: It’s been a while. Last night, auroras were sighted in more than a dozen US states after a CME struck Earth’s magnetic field. “The G2 geomagnetic storm produced the first visible auroras from coastal Massachusetts since 2017,” reports Chris Cook, who snapped this 30-second self portrait around 1am EDT on Oct. 12th:

The red-topped auroras Cook witnessed are relatively rare; they appear during geomagnetic storms that spread far from the poles. Red is caused by oxygen atoms meeting the solar wind as high as 500 km above Earth’s surface.

In some states the auroras were so bright onlookers photographed them using nothing more than their cell phones. iPhone or Android? You decide:

The iPhone photo on the left comes from Tyler Knight of Mound, Minnesota, while the Samsung Galaxy image on the right was taken by meteorologist James Sinko on Castle Hill, Maine. Across the border in Saskatoon, Canada, Frank Lang recorded a must-see video using his iPhone 12.

At the apex of the storm, auroras descended as far south as Nebraska. Caryl Bohn photographed their faint red glow from the town of West Oak.

Subscribers to our Space Weather Alert system were notified the instant the CME hit. The alert was triggered by a sudden uptick in solar wind speed signalling the arrival of a shock front:

The plot shows data from NOAA’s DSCOVR spacecraft. When the CME passed by, the solar wind quickened by 120 km/s. At the same time, the plasma density tripled, and the temperature increased almost 10-fold. These are classic signs of a direct hit by a CME.

A New Meteor Shower: The Arids

Oct. 6, 2021: For thousands of years, Comet 15P/Finlay has been dive-bombing Earth’s orbit, leaving trails of dust on our planet’s doorstep, yet, strangely, there has never been a meteor shower. Until now. On Sept. 27th, Earth hit a stream of debris from Comet Finlay, and a meteor shower was born.

Above: An Arid meteor (inset) detected by the Cerro Tololo station of the CAMS Chile network on Sept. 29. [video] [more]

“It is called the Arid meteor shower, because the meteors radiate from the far-southern constellation Ara, the Altar,” explains Peter Jenniskens of the SETI Institute, whose meteor cameras in New Zealand and Chile detected the mini-outburst of 13 Arids.

It’s long overdue. Every 6 years, Finlay passes only 0.01 au from Earth’s orbit. Somehow, we’ve dodged the debris. “This is the first time we’ve ever seen meteors from the comet,” says Jenniskens.

The shower might not be over. Earth is poised to hit another of Finlay’s debris streams, and this one could trigger a storm.

“We predict an encounter sometime between Oct. 6th at 2200 UT and Oct. 7th at 0100 UT,” says astronomer Quanzhi Ye of the University of Maryland. “Forecasts range from ~50 to as many as 1100 meteors per hour.”

The debris was ejected by the comet in 2014 and 2015. In those years, something unexpected happened. Astronomers watching Finlay dive through the inner Solar System were surprised when the comet erupted–twice–more than quadrupling in brightness and producing massive jets of gas and dust.

Above: Finlay’s outburst in 2015 from “Bangs and Meteors from the Quiet Comet 15P/Finlay” by Ye et al. (Astrophysical Journal, Oct. 2015)

“Somewhere between 100 million and a billion kilograms of material were ejected–about the mass of a small hill,” says Ye, who has spent years studying Finlay and its debris.

If Earth grazes this material, a meteor storm could occur. Unfortunately for sky watchers, the best place to see it is in Antarctica. However, the timing also favors observers in parts of South America. “Our cameras are well-positioned to record anything that happens,” says Jenniskens.

UPDATE: The newly-discovered Arid meteor shower may have just produced an outburst over Antarctica. The University of Colorado Boulder operates a shortwave meteor radar at McMurdo Sound, and it detected a significant peak in meteor activity around 2300 UT on Oct. 6th. That matches the time Earth was expected to encounter a stream of debris from parent comet 15P/Finlay.

A Gigantic Jet with Fireballs

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.”

Earth Can Make Auroras Without Solar Activity

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. (2021), Beam-driven ECH waves: A parametric study, Phys. Plasmas, 28, 072902, https://doi.org/10.1063/5.0053187

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

Inspiration 4: Historic Space Mission Blasts Off

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.

Solar Tsunami and CME

Aug. 27, 2021: Sunspot AR2859 erupted on Aug. 26th, producing a C3-class solar flare: movie. The flare, however, was not the main attraction. The eruption also caused a massive “solar tsunami.” Watch the shadowy wave ripple across the sun in this false-color ultraviolet movie from NASA’s Solar Dynamics Observatory:

The expanding circular shadow is a wave of hot plasma and magnetism. Based on the time it took to reach the next sunspot, halfway around the sun, the tsunami was traveling faster than 110,000 mph.

Solar tsumanis always herald a CME, and this one was no exception. Soon after the tsunami broke, SOHO coronagraphs detected a plasma cloud leaving the sun: movie.

Update: NOAA analysts have modeled the CME’s trajectory. They predict an Earth impact during the late hours of Aug. 29th, possibly sparking G1-class geomagnetic storms through midday on Aug. 30th.   Aurora alerts: SMS Text.

SOLAR RADIO BURST: When sunspot AR2659 exploded on Aug. 26th, shortwave loudspeakers on the dayside of Earth erupted with static. “It was a solar radio burst,” reports Thomas Ashcraft, who recorded the sounds from his observatory in rural New Mexico. Click to listen:

Take another look at the “solar tsunami,” above. Much of the static Ashcraft recorded is caused by that shock wave rippling through the sun’s atmosphere. Plasma waves in the ionized corona naturally emit radio noise. Ham radio operators, military radar installations, and radio astronomers have been picking up these sounds since the 1940s. You can do it yourself from your own backyard.

“As I write, the sun just produced another very strong radio burst, which really packed a punch on my spectrograph!” says Ashcraft. In other words, stay tuned for more…

Perseid Meteor Outburst

Aug. 18, 2021: 28 years ago, the Perseid meteor shower killed a satellite. On Aug. 11, 1993, a Perseid meteoroid hit the Olympus-1 telecommunications satellite, making it spin. The $850 million spacecraft was lost after it ran out of fuel trying to regain control.  Many researchers blame a dense ribbon of comet dust now known as “the Perseid Filament.”

This week, the Perseid Filament came back. Probably.

Above: The Perseid outburst of Aug. 14, 2021, captured by Carl Bracken of the Cedar Amateur Astronomers in Iowa using his AMS42 camera. More images.

On Aug. 14, 2021, night skies over North America filled with meteors. P.  Martin of Ottawa, Canada, reported “multiple Perseids per minute with many bursts, sometimes 3-4 in a second.” In San Diego, Robert Lunsford of the International Meteor Organization also witnessed rapidfire streaks, 2 to 3 at a time. “It made me realize something unusual was going on,” Lunsford says, “especially so far from the predicted maximum.”

To say that astronomers were surprised would be an understatement. The Perseid’s annual peak had occurred the night before. Most observers had already given up watching. Fortunately, a network of automated cameras operated by the Cedar Amateur Astronomers in Iowa captured the display. Overnight they recorded almost 3000 meteors.

Above: Meteor rates during the 2021 outburst. More.

Peter Jenniskens, an astronomer at the SETI Institute and NASA/Ames, believes it may have been the Perseid Filament. “I think so,” he says. “The width of the outburst is similar to that of past Perseid Filament returns.”

The Perseid Filament is a ribbon of dust inside the broader Perseid debris zone. Comet 109P/Swift-Tuttle supplies the raw material. The comet loops around the sun every 133 years, shedding dust as it goes. Over time, much of Swift-Tuttle’s dust is perturbed by the gravity of Jupiter, helping scatter it into the diffuse cloud that we experience every year as the Perseid meteor shower. But there is a part of the comet’s orbit in a “mean motion resonance” with Jupiter where dust can accumulate instead of dispersing. This is the Perseid Filament.

Forecasters still can’t predict when the Perseid Filament will return. It came for many years in a row around 1993, and it may have grazed Earth again, slightly, in 2018, 2019 and 2020. No one predicted a direct hit in 2021.

This uncertainty naturally raises the question: Was it really the Filament? The jury’s still out. Observers may have stumbled upon an entirely new ribbon of Perseid dust. Either way, researchers are looking forward to next year to see if it comes back again. And they probably won’t stop watching when the peak is “done.”

Blue Lightning in the Stratosphere

Aug. 15, 2021: Rain. Clouds. Thunder. The stratosphere has none of those things. Weather up there is pretty dull. Except when the lightning starts….

Researchers call them “blue jets.” The elusive discharges leap into the stratosphere from thunderstorms far below. They are rarely seen, but storm chaser Rob Neep was able to capture some over Sonora, Mexico, on August 3rd:

“I couldn’t believe my eyes,” says Neep, a former TV photojournalist. “I was actually looking for sprites when the jets appeared. They were definitely visible to the naked eye, both my cousin and I observed them.”

Oscar van der Velde of the Lightning Research Group at the Universitat Politècnica de Catalunya watched Neep’s video and says it is “Excellent–perhaps the best example of classic blue jets we’ve seen in a long time!”

First recorded by cameras on the space shuttle in 1989, blue jets are part of a growing menagerie of transient luminous events (TLEs) in the upper atmosphere. They appear alongside sprites, ELVES, and other lightning-like forms. Blue jets, however, seem to be more elusive than the others, often frustrating photographers who try to catch them.

“We’re not sure why ground-based observers see them so rarely,” says van der Velde. “It might have something to do with their blue color. Earth’s atmosphere naturally scatters blue light, which makes them harder to see. Neep’s video was taken from a relatively high altitude site (elevation 3500 ft); thin clear air probably helped.”

“Not all storms have blue jets,” he allows. “Even so, blue jets may be much more common than we think.”

Above: Artist’s concept of a blue jet observed from the ISS. Credit: DTU Space, Daniel Schmelling/Mount Visual

In 2018, SpaceX launched Europe’s Atmosphere-Space Interactions Monitor (ASIM) to the International Space Station to study TLEs from space. Data from ASIM show that blue jets can leap as high as 170,000 feet above the ground. They’re sparked by mysterious “blue bangs“–brilliant blue flashes in the tops of thunderclouds possibly caused by intense turbulence.

It’s important to study blue jets because, according to van der Velde, “there can be considerable production of NOx and ozone by these discharges, potentially affecting the chemistry of the atmosphere.” Also, some blue jets might rise high enough to touch the ionosphere, forming a new and poorly understood branch of the global electrical circuit.

And on top of everything else, “they’re beautiful,” says Neep. “I was lucky to catch some.”