Sprite Season Begins

April 7, 2021: Spring is the season for sprites, and Paul Smith just photographed a magnificent display over Kansas. “These were my first big sprites of the season,” says Smith, who took this picture on April 6th:

“They were so bright, I saw a couple of them with my unaided eyes,” he adds.

Sprites are a weird form of lightning that leap up from powerful thunderstorms. The ones Smith saw are “jellyfish sprites”, named for their resemblance to sea creatures. Their red tentacles stretch about 90 km high, almost touching the edge of space. Other forms exist, too.

At this time of year, severe storms set the stage for sprite formation. Mesoscale convective systems sweep across the Great Plains, cracking with intense electric fields that drive electrons up and into sprites. La Niña conditions in the Pacific Ocean may amplify this process.

Although the sprites were in Kansas, Smith saw them from Oklahoma. This weather satellite image shows the observing geometry.

“I was about 200 miles away from the thunderstorm,” says Smith. Turns out, that’s about the right distance. You have to be far away to see sprites over the top of the thunderclouds.

Although sprites have been reported by pilots and storm chasers for more than a century, many scientists were skeptical. Can you blame them? “Doctor, I just saw a giant red jellyfish in the sky!” A turning point came in 1989 when sprites were photographed by researchers at the University of Minnesota and cameras onboard the space shuttle. Now sprites are in the mainstream. See for yourself.

Realtime Sprite Photo Gallery
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The Chance of Storms Just Doubled

April 8, 2021: If you think you are safe from geomagnetic storms, think again. A new study just published in the journal Space Weather finds that powerful storms may be twice as likely as previously thought.

Jeffrey Love of the US Geological Survey, who authored the study, analyzed Earth’s strongest geomagnetic storms since the early 1900s. Previous studies looked back only to the 1950s. The extra data led to a surprise:

“A storm as intense as, say, the Québec Blackout of 1989 is predicted to occur, on average, about every four solar cycles. This is twice as often as estimated using only the traditional shorter dataset,” says Love.

Above: The data Love used in his extreme value analysis. Red and blue circles denote the two strongest storms in each solar cycle. Dst is a measure of geomagnetic activity that can be estimated from old magnetogram chart recordings.

A study like this is part physics, part math, and part detective work.

Love has spent recent years digging deeply into historical records, trying to figure out how often intense geomagnetic storms occur. It’s tricky. Even when old records of magnetic activity are published, they aren’t always easy to find or interpret. Love recalls the example of Vassouras, Brazil, where important magnetic data were recorded during the Great Geomagnetic Storm of May 1921:

“My colleague, Hisashi Hayakawa, discovered that a copy of the Vassouras yearbook (an annual summary of magnetic data) was held in a Japanese archive maintained by the World Data Center in Kyoto. In that yearbook is a copy of the magnetogram we needed. It is in fragments, upside down, and mislabeled, all of which had to be sorted out. I digitized it myself, and we were able to use the data to estimate the intensity of the 1921 storm.”

Above: A mixed-up fragment of a 1921 magnetogram chart recording from Vassouras, Brazil.

Tricky indeed. Love did similar digging for other storms as far back as Solar Cycle 14, which peaked in 1906. Ultimately, he was able to piece together a list of the most intense events. The top two storms of each solar cycle formed his dataset.

Then the statistics began. The methods Love used are not new, per se, but they are new to the field of space weather. Love explains: “Extreme-value statistical methods were developed by statisticians in the 1920s to 1940s. From there, it took a while for the methods to be distilled down and presented in an approachable way for non-statisticians. They are really only now starting to be used in the space weather community.”

Above: The morning after–a March 14, 1989, report of the Great Quebec Blackout in Montreal’s newspaper, the Gazette. [more]

An important result of Love’s research is the odds of another Québec-class storm: On March 13, 1989, a coronal mass ejection (CME) slammed into Earth’s magnetic field. It hit with unusual force, because a previous CME had cleared a path for it. Within 90 seconds of impact, the Hydro-Québec power grid failed, plunging millions of Canadians into darkness.

As the geomagnetic storm intensified, bright auroras spread as far south as Florida, Texas, and Cuba. Some onlookers thought they were witnessing a nuclear exchange. Decades later, power grid operators are still figuring out how to protect their systems from a repeat calamity.

Québec was once thought to be a 100 year storm. Extreme value statistics suggest a different answer. “It’s more like 45 years,” says Love.

In other words, the chance of storms just doubled.

Love’s original research, entitled “Extreme-event magnetic storm probabilities derived from rank statistics of historical Dst intensities for solar cycles 14-24,” may be read here.

20 Years Ago, An Extreme Geomagnetic Storm

March 31, 2021: What a difference 20 years makes. Today the sun is blank and featureless as Solar Cycle 25 struggles pull solar activity from the doldrums of a deep Solar Minimum. In March 2001, however, the solar disk was peppered with sunspots, including a monster named “AR9393.” The biggest sunspot of Solar Cycle 23, AR9393 was a truly impressive sight, visible to the naked eye at sunset and crackling with X-class solar flares.

On March 29, 2001, AR9393 hurled a pair of CMEs directly toward Earth. The first one struck during the early hours of March 31, 2001. The leading edge of the shock front was dense (~150 protons/cc) and strongly magnetized — traits that give rise to powerful geomagnetic disturbances. Within hours, an extreme geomagnetic storm was underway, registering the maximum value of G5 on NOAA storm scales.

“I was fortunate to witness and photograph the event when I was just a teenager,” recalls Lukasz Gornisiewicz, who watched the show from Medicine Hat, Alberta:

In the hours that followed, Northern Lights spread as far south as Mexico. In 20 year old notes, Dr. Tony Phillips of Spaceweather.com describes “red and green auroras dancing for hours” over the Sierra Nevada mountains of California at latitude +37 degrees. Similar displays were seen in Houston, Texas; Denver Colorado; and San Diego, California.

“Here in Payson, Arizona, red curtains and green streamers were pulsating all across the sky,” wrote Dawn Schur when she submitted this picture to Spaceweather.com 20 years ago:

“We have seen some auroras here before, but this display was really special,” she wrote.

A second CME struck at ~2200 UT on March 31th. Instead of firing up the storm, however, the impact quenched it. When the CME passed Earth the interplanetary magnetic field surrounding our planet suddenly turned north — an unfavorable direction for geomagnetic activity.

Indeed, the quenching action of the second CME may have saved power grids and other technological systems from damage. The storm’s intensity (-Dst=367 nT) stopped just short of the famous March 14, 1989, event that caused the Quebec Blackout (-Dst=565 nT) and it was only a fraction of the powerful Carrington Event of 1859 (-Dst=~900 nT).

The whole episode lasted barely 24 hours, brief but intense. Visit Spaceweather.com archives for March 30, 31st and April 1, 2001, to re-live the event. Our photo gallery from 20 years ago is a must-see; almost all the pictures were taken on film!

March 30-31, 2001, Aurora Photo Gallery
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Einstein’s Eclipse

March 26, 2021: On May 29, 1919, the Moon slid in front of the sun and forever altered our understanding of spacetime. It was “Einstein’s Eclipse.” Using the newly-developed theory of relativity, the young German physicist predicted that the sun’s gravity should bend starlight–an effect which could be seen only during a total eclipse. Some of the greatest astronomers of the age rushed to check his prediction.

More than 100 years later, Petr Horálek (ESO Photo Ambassador, Institute of Physics in Opava) and Miloslav Druckmüller (Brno University of Technology) have just released a stunning restoration of the photo that proved Einstein right:

The original picture was taken in May 1919 by astronomers Andrew Crommelin and Charles Rundle Davidson, who traveled from the Greenwich Observatory in London to the path of totality in Sobral, Brazil. They were part of a global expedition organized in part by Sir Arthur Eddington, who wanted to test Einstein’s strange ideas. Glass photographic plates from the expedition were typical of early 20th century astrophotography, colorless and a little dull.

“Our restoration shows how the eclipse would have been recorded today–a magnificent sight,” says Horálek. “The astronomers in Brazil must have been amazed when they saw the giant prominence with their unaided eyes.”

Above: From the report of Sir Arthur Eddington, a half-tone reproduction of one of the negatives taken with the 4-inch lens at Sobral, Brazil.

Horálek got the idea for this restoration in 2019 when he saw a partially restored image released by the ESO (European Southern Observatory) to celebrate the 100th anniversary of the eclipse. A scan of the original plate was provided by the Heidelberg Digitized Astronomical Plates project … and then the real work began.

“I started by manually removing scratches and specks of dust from the copied plate,” says Horálek. “There were dozens of them, and the whole process took about 50 hours of work.”

Next, Horálek applied Noise Adaptive Fuzzy Equalization (NAFE) software to sharpen the remaining details. NAFE was developed by Prof. Druckmüller to enhance images from NASA’s Solar Dynamics Observatory. It worked marvelously on the old eclipse, revealing delicate streamers and hints of a dipole structure in the sun’s corona.

Finally, he added color. “I created a palette to make the image as natural as possible. The sun’s corona is white because it is sunlight scattered by free electrons. The prominence has that special red color (H-alpha) which hydrogen makes in the sun’s atmosphere. Once these two colors were fixed, the dark-blue hue of the background sky emerged naturally. Voilà!–a modern view of Einstein’s eclipse.”

Meanwhile, back in 1919, the eclipse was a sensation. Eddington measured the positions of stars near the sun during the eclipse. (Two of them, 65 and 67 Tauri, may be found in the bottom right of the restoration.) They were displaced just as Einstein predicted. Spacetime really was a fabric that could be stretched.

The result was splashed across the front pages of most major newspapers. It made Einstein and his theory of general relativity world-famous. Einstein has been quoted as describing his reaction if general relativity had not been confirmed by Eddington and Dyson in 1919: “Then I would feel sorry for the dear Lord. The theory is correct anyway.”

“2021 is the 100th anniversary of Einstein’s Nobel Prize,” notes Horálek. “This photo is our way of paying tribute to his work.”

Full credit: ESO/Landessternwarte Heidelberg-Königstuhl/F. W. Dyson, A. S. Eddington, & C. Davidson, P. Horálek/Institute of Physics in Opava, M. Druckmüller.

The Great Québec Blackout

March 13, 2021: They call it “the day the sun brought darkness.” On March 13, 1989, a powerful coronal mass ejection (CME) hit Earth’s magnetic field. Ninety seconds later, the Hydro-Québec power grid failed. During the 9 hour blackout that followed, millions of Quebecois found themselves with no light or heat, wondering what was going on?

“It was the biggest geomagnetic storm of the Space Age,” says Dr. David Boteler, head of the Space Weather Group at Natural Resources Canada. “March 1989 has become the archetypal disturbance for understanding how solar activity can cause blackouts.”

Above: Sunspot 5395, source of the March 1989 solar storm. From “A 21st Century View of the March 1989 Magnetic Storm” by D. Boteler.

It seems hard to believe now, but in 1989 few people realized solar storms could bring down power grids. The warning bells had been ringing for more than a century, though. In Sept. 1859, a similar CME hit Earth’s magnetic field–the infamous “Carrington Event“–sparking a storm twice as strong as March 1989. Electrical currents surged through Victorian-era telegraph wires, in some cases causing sparks and setting telegraph offices on fire. These were the same kind of currents that would bring down Hydro-Québec.

“The March 1989 blackout was a wake-up call for our industry,” says Dr. Emanuel Bernabeu of PJM, a regional utility that coordinates the flow of electricity in 13 US states. “Now we take geomagnetically induced currents (GICs) very seriously.”

What are GICs? Freshman physics 101: When a magnetic field swings back and forth, electricity flows through conductors in the area. It’s called “magnetic induction.” Geomagnetic storms do this to Earth itself. The rock and soil of our planet can conduct electricity. So when a CME rattles Earth’s magnetic field, currents flow through the soil beneath our feet.

Above: Grey areas indicate regions of igneous rock where power grids are most vulnerable to geomagnetic storms.

Québec is especially vulnerable. The province sits on an expanse of Precambrian igneous rock that does a poor job conducting electricity. When the March 13th CME arrived, storm currents found a more attractive path in the high-voltage transmission lines of Hydro-Québec. Unusual frequencies (harmonics) began to flow through the lines, transformers overheated and circuit breakers tripped.

After darkness engulfed Quebec, bright auroras spread as far south as Florida, Texas, and Cuba. Reportedly, some onlookers thought they were witnessing a nuclear exchange. Others thought it had something to do with the space shuttle (STS-29), which remarkably launched on the same day. The astronauts were okay, although the shuttle did experience a mysterious problem with a fuel cell sensor that threatened to cut the mission short. NASA has never officially linked the sensor anomaly to the solar storm.

Much is still unknown about the March 1989 event. It occurred long before modern satellites were monitoring the sun 24/7. To piece together what happened, Boteler has sifted through old records of radio emissions, magnetograms, and other 80s-era data sources. He recently published a paper in the research journal Space Weather summarizing his findings — including a surprise:

“There were not one, but two CMEs,” he says.

The sunspot that hurled the CMEs toward Earth, region 5395, was one of the most active sunspot groups ever observed. In the days around the Quebec blackout it produced more than a dozen M- and X-class solar flares. Two of the explosions (an X4.5 on March 10th and an M7.3 on March 12th) targeted Earth with CMEs.

“The first CME cleared a path for the second CME, allowing it to strike with unusual force,” says Boteler. “The lights in Québec went out just minutes after it arrived.”

Above: Auroras over Pershore, England, during the March 13, 1989, geomagnetic storm. Credit: Geoffrey Morley.

Among space weather researchers, there has been a dawning awareness in recent years that great geomagnetic storms such as the Carrington Event of 1859 and The Great Railroad Storm of May 1921 are associated with double (or multiple) CMEs, one clearing the path for another. Boteler’s detective work shows that this is the case for March 1989 as well.

The March 1989 event kicked off a flurry of conferences and engineering studies designed to fortify grids. Emanuel Bernabeu’s job at PJM is largely a result of that “Québec epiphany.” He works to protect power grids from space weather — and he has some good news.

“We have made lots of progress,” he says. “In fact, if the 1989 storm happened again today, I believe Québec would not lose power. The modern grid is designed to withstand an extreme 1-in-100 year geomagnetic event. To put that in perspective, March 1989 was only a 1-in-40 or 50 year event–well within our design specs.”

Some of the improvements have come about by hardening equipment. For instance, Bernabeu says, “Utilities have upgraded their protection and control devices making them immune to type of harmonics that brought down Hydro-Québec. Some utilities have also installed series capacitor compensation, which blocks the flow of GICs.”

Other improvements involve operational awareness. “We receive NOAA’s space weather forecast in our control room, so we know when a storm is coming,” he says. “For severe storms, we declare ‘conservative operations.’ In a nutshell, this is a way for us to posture the system to better handle the effects of geomagnetic activity. For instance, operators can limit large power transfers across critical corridors, cancel outages of critical equipment and so on.”

The next Québec-level storm is just a matter of time. In fact, we could be overdue. But, if Bernabeu is correct, the sun won’t bring darkness, only light.

Additional reading:

A 21st Century View of the March 1989 Magnetic Storm” by David Boteler, head of the Space Weather Group at Natural Resources Canada.

Geomagnetically induced currents: Science, engineering, and applications readiness” by Antti Pulkkinen (NASA/GSFC), Emanuel Bernabeu (PJM) and many others.

Ham Radio Signals from Mars

Feb. 16, 2021: Around the world, ham radio operators are doing something once reserved for national Deep Space Networks. “We’re monitoring spacecraft around Mars,” says Scott Tilley, of Roberts Creek, British Columbia, who listened to China’s Tianwen-1 probe go into orbit on Feb. 10th. The signal, which Tilley picked up in his own back yard, was “loud and audible.”  Click to listen:

The signal from Tianwen-1 is dominated by a strong X-band carrier wave with weaker side bands containing the spacecraft’s state vector (position and velocity). Finding this narrow spike of information among all the possible frequencies of deep space communication was no easy task.

“It was a bit like a treasure hunt,” Tilley says. “Normally a mission like this would have its frequency published by the ITU (International Telecommunications Union). China did make a posting, but it was too vague for precise tuning. After Tianwen-1 was launched, observers scanned through 50MHz of spectrum and found the signal. Amateurs have tracked the mission ever since with great accuracy thanks to the decoded state vector from the probe itself.”

So far, Tilley has picked up signals from China’s Tianwen-1 spacecraft, NASA’s Mars Reconnaissance Orbiter, and the United Arab Emirates’ Hope probe–all orbiting Mars approximately 200 million kilometers away. How is such extreme DX’ing possible?

“It helps to have a big antenna,” says Tilley, who uses a 60 cm dish, pictured above. “But the real key,” he says, “is the advent of Software Defined Radios (SDRs) , which have become the norm for hams in the past decade or so.”

In a Software Defined Radio, computers digitally perform the signal mixing and amplification functions of circuits that used to be analog. SDRs are cheap, sensitive, and they give hams the kind of exquisite control over frequency required to tune into distant spacecraft.

“Amateurs really began listening to deep space probes in the late 1990s and early 2000s,” says Tilley. “This sparked an awareness that it was possible. The combination of improving technology and growing awareness has resulted in more and more interplanetary detections.”

Next up: NASA’s Mars 2020 spacecraft carrying the Perseverance rover, due to reach Mars Feb. 18th:

Tilley plans to listen but he doesn’t expect a strong signal. “Perseverance does not have a very large antenna,” says Tilley. “It doesn’t need one because it can use other NASA spacecraft in Mars orbit as relays. The signal will therefore be weak and I doubt many amateurs will record the landing in Jezero crater.”

Tianwen-1, on the other hand, has a relatively large antenna with a booming signal. “China probably plans to use it as a relay for future Chinese space missions,” Tilley speculates. “This makes it a good target for hams hoping to bag their first Martian spacecraft.”

Stay tuned for more radio signals from Mars.

A New Form of Space Weather: Earth Wind

Feb. 12, 2021: The sun is windy. Every day, 24/7, a breeze of electrified gas blows away from the sun faster than a million mph. Solar wind sparks beautiful auroras around the poles of Earth, sculpts the tails of comets, and scours the surface of the Moon.

Would you believe, Earth is windy, too? Our own planet produces a breeze of electrified gas. It’s like the solar wind, only different, and it may have important implications for space weather on the Moon.

“Earth wind” comes from the axes of our planet. Every day, 24/7, fountains of gas shoot into space from the poles. The leakage is tiny compared to Earth’s total atmosphere, but it is enough to fill the magnetosphere with a riot of rapidly blowing charged particles. Ingredients include ionized hydrogen, helium, oxygen and nitrogen.

Once a month, the Moon gets hit by a blast of Earth wind. It happens around the time of the full Moon when Earth’s magnetic tail points like a shotgun toward the lunar disk. For 3 to 5 days, lunar terrain is bombarded by H+, He+, O+, N2+ and other particles.

One effect of Earth wind, just discovered, is to create water. According to a new study published in the January 2021 edition of the Astrophysical Journal Letters, Earth wind can actually make H2O on the lunar surface.

“Hydrogen ions in Earth wind combine with oxygen in Moon rocks and soil to make hydroxyl (OH) and water (H2O),” explains one of the lead authors, Quanqi Shi of Shandong University and the Chinese Academy of Sciences. “This came as a surprise.”

Above: An artist’s concept of Earth wind (blue)

Researchers have long known that hydrogen from space raining down on the Moon can create a temporary form of surface water. Solar wind does it all the time. However, this kind of water was expected to dry up once a month when the Moon enters Earth’s magnetic tail. Terrestrial magnetism deflects solar wind, turning the faucet to the OFF position.

But that’s not what happened.

The researchers looked at data from NASA’s Moon Mineralogy Mapper (M3) onboard India’s Chandrayaan-1 spacecraft, which was orbiting the Moon in 2009 when the Moon made multiple passes through Earth’s magnetic tail.  “We found that lunar surface water does not disappear as expected during the magnetosphere shielding period,” says Shi. “Earth wind must be bridging the gap.”

Above: Sample Chandrayaan-1 observations of lunar surface water [more]

In fact, when it comes to producing water, Earth wind has some big advantages over solar wind. When the full Moon is inside Earth’s magnetic tail, it is surrounded by Earth wind and feels its impact from every direction. The lunar nearside, lunar farside, and lunar poles are all peppered with Earth wind particles. In this sense, Earth wind can potentially make water anywhere–unlike the solar wind which rains down only on the lunar dayside.

Another potential advantage of Earth wind: It is oxygen rich, much more so than solar wind. “Oxygen is another key element of water,” points out Shi. “Whether these oxygen ions can contribute to the formation of lunar water is a very intriguing question for future study.”

Want to learn more? Read the original research here: “Earth Wind as a Possible Exogenous Source of Lunar Surface Hydration

Co-rotating Interaction Region Sparks Auroras

Feb. 3, 2021: What made the auroras of Feb. 2nd so good? It was a co-rotating interaction region (CIR). CIRs are transition zones between slow- and fast-moving streams of solar wind. Solar wind plasma piles up in these regions, creating density gradients and shock waves that can rock Earth’s magnetic field much like a coronal mass ejection (CME).

A CIR hit Earth on Feb. 2nd and “the lights were incredible–just fantastic,” reports aurora tour guide Marianne Bergli who witnessed the display from a beach near Tromsø, Norway:

“Every color in the heavens cycled through the sky,” she says. “It. Was. Amazing.”

CIRs are a way for the sun to spark auroras without explosive solar activity. All that’s required is a fast solar wind stream brushing up against a slower one. In the transition zone, thick rivulets of plasma press magnetic fields together, creating strong shock-like structures that mimic CMEs. Indeed, some forecasters refer to co-rotating interaction regions as “mini-CMEs.”

Says Bergli, “I am looking forward to the next one!”

What if … A Perfect CME Hit Earth?

Jan. 21, 2021: You’ve heard of a “perfect storm.” But what about a perfect solar storm? A new study just published in the research journal Space Weather considers what might happen if a worst-case coronal mass ejection (CME) hit Earth. Spoiler alert: You might need a backup generator.

For years, researchers have been wondering, what’s the worst the sun could do? In 2014, Bruce Tsurutani (JPL) and Gurbax Lakhina (Indian Institute of Geomagnetism) introduced the “Perfect CME.” It would be fast, leaving the sun around 3,000 km/s, and aimed directly at Earth. Moreover, it would follow another CME, which would clear the path in front of it, allowing the storm cloud to hit Earth with maximum force.

None of this is fantasy. The Solar and Heliospheric Observatory (SOHO) has observed CMEs leaving the sun at speeds up to 3,000 km/s. And there are many documented cases of one CME clearing the way for another. Perfect CMEs are real.

Using simple calculations, Tsurutani and Lakhina showed that a Perfect CME would reach Earth in only 12 hours, allowing emergency managers little time to prepare, and slam into our magnetosphere at 45 times the local speed of sound. In response to such a shock, there would be a geomagnetic storm perhaps twice as strong as the Carrington Event of 1859. Power grids, GPS and other high-tech services could experience significant outages.

Sounds bad? Turns out it could be worse.

In 2020, a team of researchers led by physicist Dan Welling of the University of Texas at Arlington took a fresh look at Tsurutani and Lakhina’s Perfect CME. Space weather modeling has come a long way in the intervening 6 years, so they were able to come to new conclusions.

“We used a coupled magnetohydrodynamic(MHD)-ring current-ionosphere computer model,” says Welling. “MHD results contain far more complexity and, hopefully, better reflect the real-world system.”

Above: Sample results from computer modeling a Perfect CME impact. The images show the distortion and compression of Earth’s magnetic field as well as induced currents in the atmosphere. Source: Welling et al, 2020.

The team found that geomagnetic disturbances in response to a Perfect CME could be 10 times stronger than Tsurutani and Lakhina calculated, particularly at latitudes above 45 to 50 degrees. “[Our results] exceed values observed during many past extreme events, including the March 1989 storm that brought down the Hydro-Quebec power grid in eastern Canada; the May 1921 railroad storm; and the Carrington Event itself,” says Welling.

A key result of the new study is how the CME would distort and compress Earth’s magnetosphere. The strike would push the magnetopause down until it is only 2 Earth-radii above our planet’s surface. Satellites in Earth orbit would suddenly find themselves exposed to a hail of energetic charged particles, potentially short-circuiting sensitive electronics. A “superfountain” of oxygen ions rising up from the top of Earth’s atmosphere might literally drag satellites down, hastening their demise. (Note: Welling’s group stopped short of modelling the superfountain.)

For specialists, Table 1 from Welling et al’s paper compares their simulation of a Perfect CME impact (highlighted in yellow) to past extreme events:

You don’t have to understand all the numbers to get the gist of it. A Perfect CME strike would dwarf many previous storms.

Now for the good news: Perfect CMEs are rare.

Angelos Vourlidas of Johns Hopkins University has studied the statistics of CMEs. He notes that SOHO has captured only two CMEs with velocities greater than 3,000 km/s since the start of operations in 1996. “This means we expect roughly one CME ejected at speeds above 3000 km/s per solar cycle,” he says.  Speed isn’t the only factor, however. To be “perfect,” a 3000 km/s CME would need to follow another CME, clearing its path, and both CMEs must be aimed directly at Earth.

It all adds up to something that doesn’t happen every day. But one day, it will happen. As Welling et al conclude in their paper, “Further exploring and preparing for such extreme activity is important to mitigate space-weather related catastrophes.”

Read the original research here.

A Musical Note from the Magnetosphere

Jan. 19, 2021: High above the Arctic Circle in Lofoten, Norway, citizen scientist Rob Stammes operates a space weather monitoring station. His sensors detect ground currents, auroras, radio bursts, and disturbances in Earth’s magnetic field. Yesterday, he says, “I received a musical note from the magnetosphere.”

“Around 05.30 UTC on Jan. 18th, our local magnetic field began to swing back and forth in a rhythmic pattern,” he says. “Electrical currents in the ground did the same thing. It was a nearly pure sine wave–like a low frequency musical note. The episode lastesd for more than 2 hours.”

Stammes has received such notes before, but they are rare. “I see a pattern like this only about once a year,” he says.

Space physicists call this phenomenon a “pulsation continuous” or “Pc” for short. Imagine blowing across a piece of paper, making it flutter with your breath. Solar wind does the same thing to magnetic fields. Pc waves are essentially flutters propagating down the flanks of Earth’s magnetosphere excited by the breath of the sun.

Above: A magnetometer in Abisko, Sweden, recorded the same waves

Yesterday’s set of waves washed over Norway and Sweden, but almost nowhere else, according to the global INTERMAGNET network of magnetometers. It was a strictly regional phenomenon.

What happens in the sky when such a pure tone emerges from the natural background cacophony of magnetic activity? “I wish I knew,” says Stammes. “I was asleep at the time.” In fact, it’s possible that no one knows. Tones like these are rare, and they all too often occur while skies are cloudy or daylit, blocking any peculiar auroras from view. Stammes says he plans to build an alert system to help him find out. No pun intended: Stay tuned.