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.

Noctilucent Clouds over Argentina

Jan. 8, 2021: They’re back. Noctilucent clouds (NLCs), recently missing, are once again circling the South Pole. And, in an unexpected twist, they’ve just appeared over Argentina as well.

“This is a very rare event,” reports Gerd Baumgarten of Germany’s Leibniz-Institute of Atmospheric Physics, whose automated cameras caught the meteoritic clouds rippling over Rio Grande, Argentina (53.8S) on Jan. 3rd:

A second camera recorded the clouds at even higher latitude: Rio Gallegos (51.6S). At this time of year, noctilucent clouds are supposed to be confined to the Antarctic–not Argentina. In the whole history of atmospheric research, NLCs have been sighted at mid-southern latitudes only a handful of times.

“Personally, I am thrilled to see NLCs in Argentina, as I had not expected them to occur so far north,” says Natalie Kaifler of the German Aerospace Center (DLR), who operates a lidar (laser radar) alongside one of Baumgarten’s cameras.

Kaifler’s lidar “pinged” the clouds during the display and confirmed that they are genuine NLCs. Echoes pinpointed their altitude more than 80 km above Earth’s surface:

Above: The ~hour-long oscillations in these lidar echoes may be caused by gravity waves propagating upward from the Andes 82 km below.

NLCs are Earth’s highest clouds. They form when summertime wisps of water vapor rise up from the poles to the edge of space. Water crystallizing around specks of meteor dust ~83 km above Earth’s surface create beautiful electric-blue structures, typically visible from November to February in the south, and May to August in the north.

This season has been unusual, though. The normal onset of NLCs over the South Pole has been delayed for more than a month as strange weather patterns played out above Antarctica. Now, suddenly, they’re back, and showing up in unexpected places.

Baumgarten has set up two cameras in southern Argentina to catch unexpected NLCs. “If it happens again,” he says, “we’ll let you know.” Stay tuned!

Noctilucent Clouds are Missing

Dec. 28, 2020: Something strange is happening 50 miles above Antarctica. Or rather, not happening. Noctilucent clouds (NLCs), which normally blanket the frozen continent in December, are almost completely missing. These images from NASA’s AIM spacecraft compare Christmas Eve 2019 with Christmas Eve 2020:

“The comparison really is astounding,” says Cora Randall of the University of Colorado’s Laboratory for Atmospheric and Space Physics. “Noctilucent cloud frequencies are close to zero this year.”

NLCs are Earth’s highest clouds. They form when summertime wisps of water vapor rise up from the poles to the edge of space. Water crystallizing around specks of meteor dust 83 km (~50 miles) above Earth’s surface creates beautiful electric-blue structures, typically visible from November to February in the south, and May to August in the north.

A crucial point: Noctilucent clouds form during summer. And that’s the problem. Although summer officially started in Antarctica one week ago, the southern stratosphere still seems to think it’s winter. In particular, the stratospheric polar vortex, which should be breaking up around now, is stubbornly hanging on. The polar vortex chokes off gravity waves, which would normally carry water vapor into the upper atmosphere. Without water vapor, NLCs cannot form.

Above: These plots of ozone hole size and zonal wind speed highlight unusual conditions in the southern stratosphere in Dec. 2020.

“The southern hemisphere stratosphere is very unusual this year,” says Randall. “The ozone hole is exceptionally large, until recently zonal winds have been blowing in the wrong direction, and overall the stratosphere is much more ‘winter-like’ than it should be in December.”

Eventually, the stratosphere will shift into its summer-like state, and NLCs can begin to blossom. But when? Researchers don’t know. If the clouds remain suppressed only one more week, it will break previous records of low NLC activity in the southern hemisphere. Stay tuned for updates right here on Spaceweather.com.

UPDATE: How do you make noctilucent clouds appear? Publish a story called “Noctilucent Clouds are Missing.” Hours after publication of this news item, NASA’s AIM satellite reported an uptick of NLC activity over Antarctica. “It’s still nowhere as many clouds as last year, but it makes sense given the recent steep drop in zonal wind speed and ozone hole area,” notes Randall. “The atmosphere definitely has a mind of its own this season!”

Weak Impact: The CME That Failed

Dec. 10, 2020: As predicted, a CME (pictured below) hit Earth’s magnetic field during the early hours of Dec. 10th (1:30 UT), but the impact did not cause a geomagnetic storm. Why not? Scroll down for the answer:

Why didn’t the CME cause a storm? Every CME brings with it some magnetic field from the sun. If that magnetic field points south, it opens cracks in Earth’s magnetic field, allowing solar wind to flow inside and fuel auroras. On the other hand, if the CME’s magnetic field points north, it seals cracks in Earth’s magnetic field, blocking the solar wind and quenching storms.

This CME brought a storm-killing north magnetic field. So, even though the velocity of the solar wind in the CME’s wake flirted with a high value of 600 km/s, it was ineffective at causing geomagnetic storms and auroras.

Maybe next time. Solar activity is picking up with the onset of new Solar Cycle 25. This is just the first of many CMEs likely to head our way in the months ahead. Aurora alerts: SMS Text.

Great Conjunction of Jupiter and Saturn

Dec. 7, 2020: Something special is happening in the sunset sky. It’s a Great Conjunction of Jupiter and Saturn. The two giant planets are converging for a close encounter the likes of which have not been seen since the Middle Ages. Shahrin Ahmad of Kuala Lumpur, Malaysia, photographed the pair on Dec. 7th:

“Jupiter and Saturn are about 1.5º apart this evening, ” says Ahmad. “Even under a light polluted sky, both can easily be seen.”

They’re about to get much closer. On Dec. 21st, the two planets will lie just 0.1 degrees apart. That’s so close, some people will perceive them as a single brilliant star. Viewed through binoculars or a small telescope, ringed Saturn will appear as close to Jupiter as some of Jupiter’s moons:

Although Great Conjunctions between Jupiter and Saturn occur every 20 years, they’re not all easy to see. Often the two planets are hidden in the glare of the sun. This year is special because the conjunction happens comfortably away from the sun. In fact, the last time the two worlds were so close together *and* so easy to see was the year 1226, astronomer Michael Brown told the Washington Post.

The show is underway. Jupiter and Saturn are already a tight pair in the evening sky, and they will grow rapidly and noticeably closer together every night for the next two weeks. Dates of special interest include Dec. 16th and 17th, when the crescent Moon joins the planets, and, of course, Dec. 21st when they are almost touching. Sky maps: Dec. 16, 17; Dec. 21.

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Strange Antarctic Weather Extends to the Edge of Space

Dec. 2, 2020: Consider it the tip of the iceberg. Noctilucent clouds (NLCs) over the south pole are AWOL.

“Normally we see the first NLCs of the southern season around Nov. 21st,” says Cora Randall of the University of Colorado’s Laboratory for Atmospheric and Space Physics (LASP). “But this year, it’s already December and we’re still waiting.”

Above: What a different one year makes. NASA’s AIM spacecraft took these pictures of NLCs over Antarctica on Nov. 29, 2019 (left) and Nov. 29, 2020 (right)

Missing NLCs is just one of the curious weather patterns currently underway at the southern end of our planet.

Making a list: (1) Earth’s southern ozone hole is not only open, but also the biggest it’s ever been in December. (2)  The air above Antarctica is currently at record cold levels for this time of year–the result of an icy polar vortex that refuses to break up. (3) In the stratosphere, east-west winds at 60 degrees South are blowing at record speed. From top to bottom, the Antarctic atmosphere is in a quirky state.

Lynn Harvey, also at LASP, gathered these plots from the Goddard Space Flight Center showing some of the unusual meteorology:

Current conditions are circled in yellow. The ozone hole (left) and stratospheric winds (right) are both setting records for this time of year.

“Based on the trends, I would say noctilucent clouds might not appear until mid-December, which is pretty unusual,” says Harvey.

NLCs are Earth’s highest clouds. They form when summertime wisps of water vapor rise up from the poles to the edge of space. Water crystallizing around specks of meteor dust 83 km above Earth’s surface creates beautiful electric-blue structures, typically visible from November to February in the south, and May to August in the north. Their appearance over Antarctica in 2020 is now seriously overdue.

What’s causing the delay? “I would guess it’s ocean/atmosphere coupling,” speculates Randall. “La Nina strengthened in October, and this is known to affect large-scale circulation in the atmosphere (e.g., Butler et al., 2011; Lin & Qian, 2019).”

“It’s blowing the scale away this year,” says Hampton University professor James Russell, principal investigator for NASA’s AIM spacecraft, which monitors noctilucent clouds. “I can’t wait to see what happens next.”

Stay tuned!

Major Solar Flare and CME

Nov. 30, 2020: Yesterday (Nov. 29th at 1311UT), Earth-orbiting satellites detected the biggest solar flare in more than 3 years. NASA’s Solar Dynamics Observatory recorded this extreme-ultraviolet movie of the M4.4 category blast:

X-rays and UV radiation from the flare ionized the top of Earth’s atmosphere, producing a shortwave radio blackout over the South Atlantic: map. Ham radio operators and mariners may have noticed strange propagation effects at frequencies below 20 MHz, with some transmissions below 10 MHz completely extinquished.

Remarkably, this flare was even bigger than it seems. The blast site is located just behind the sun’s southeastern limb. As a result, the explosion was partially eclipsed by the body of the sun. It might have been an X-class event.

The flare also hurled a significant coronal mass ejection (CME) into space, shown here in a coronagraph movie from the Solar and Heliospheric Observatory (SOHO):

Update: At first it appeared that the CME would completely miss Earth. However, NOAA analysts believe that the outskirts of the cloud might deliver a glancing blow to Earth’s magnetic field on Dec. 1-2. If so, the impact could spark a minor G1-class geomagnetic storm with auroras over northern countries such as Canada, Iceland, Norway and Sweden.

It would be a different story if the main body of the CME hit. Then we would be anticipating a strong geomagnetic storm. Maybe next time!

“Next time” could be just days away. The hidden sunspot that produced this major event will rotate onto the Earthside of the sun during the next 24 hours or so. Then its ability to spark geomagnetic storms will be greatly increased. Instant solar flare alerts: SMS Text.

Little Green Cannonballs of Light

Nov. 22, 2020: Just when you thought STEVE couldn’t get any weirder. A new paper published in the journal AGU Advances reveals that the luminous purple ribbon we call “STEVE” is often accompanied by green cannonballs of light that streak through the atmosphere at 1000 mph.

“Citizen scientists have been photographing these green streaks for years,” says Joshua Semeter of Boston University, lead author of the study. “Now we’re beginning to understand what they are.”

STEVE is a recent discovery. It looks like an aurora, but it is not. The purple glow is caused by hot (3000 °C) rivers of gas flowing through Earth’s magnetosphere faster than 13,000 mph. This distinguishes it from auroras, which are ignited by energetic particles raining down from space. Canadian aurora watchers first called attention to the phenomenon about 10 years ago, whimsically naming it STEVE; researchers have been studying it ever since.

There’s a dawning realization that STEVE is more than just a purple ribbon. Photographers often catch it flowing over a sequence of vertical pillars known as the “picket fence.” They’re not auroras either. And, now, Semeter’s team has identified yet another curiosity in their paper, entitled “The Mysterious Green Streaks Below STEVE.”

“Beneath the picket fence, photographers often catch little horizontal streaks of green light,” explains Semeter. “This is what we studied in our paper.”

Semeter’s team gathered pictures of the streaks taken by citizen scientists in Canada, the United States and New Zealand. In some cases, the same streaks were photographed by widely-separated photographers, allowing a triangulation of their position. Analyzing dozens of high-quality images, the researchers came to these conclusions:

1. The streaks are not streaks. They are actually point-like balls of gas moving horizontally through the sky. In photos, the ‘green cannonballs’ are smeared into streaks by the exposure time of the cameras.

2. The cannonballs are typically 350 meters wide, and located about 105 km above Earth’s surface.

3. The color of the cannonballs is pure green–much moreso than ordinary green auroras, reinforcing the conclusion that they are different phenomena.

Above: The pure green of STEVE’s cannonballs (upper left) is compared to the blue-green and other mixed colors of auroras. Credit: Joshua Semeter, Boston University

So, what are the cannonballs? Semeter believes they are a sign of turbulence. “During strong geomagnetic storms, the plasma river that gives rise to STEVE flows at extreme supersonic velocities. Turbulent eddies and whirls dump some of their energy into the green cannonballs.”

This idea may explain their pure color. Auroras tend to be a mixture of hues caused by energetic particles raining down through the upper atmosphere. The ‘rain’ strikes atoms, ions, and molecules of oxygen and nitrogen over a wide range of altitudes. A hodge-podge of color naturally results from this chaotic process. STEVE’s cannonballs, on the other hand, are monochromatic. Local turbulence excites only oxygen atoms in a relatively small volume of space, producing a pure green at 557.7 nm; there is no mixture.

“It all seems to fit together, but we still have a lot to learn,” says Semeter. “Advancing this physics will benefit greatly from the continued involvement of citizen scientists.”

If you’re an aurora photographer looking to contribute, be sure to read Semeter et al’s original research at https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020AV000183.

Bright Comet Erasmus

Nov. 21, 2020: Every 2000 years, Comet Erasmus (C/2020 S3) visits the inner Solar System. News Flash: It’s back. Discovered on Sept. 17, 2020, by South African astronomer Nicolas Erasmus, the dirty snowball is plunging toward the sun for a close encounter inside the orbit of Mercury on Dec. 12th. This is what it looks like:

Gerald Rhemann took the picture Friday morning, Nov. 20th, using a 12-inch telescope in Farm Tivoli, Namibia. “The tail is magnificent,” he says. “In fact, I couldn’t fit it in a single field of view. This two-panel composite shows the first 3 degrees–and it keeps going well past the edge of the photo.”

Comet Erasmus is brightening as it approaches the sun. Right now it is 7th magnitude–an easy target for backyard telescopes. Forecasters believe it will more than triple in brightness to 5th magnitude by the time it dips inside the orbit of Mercury next month. Only the glare of the nearby sun will prevent it from being visible to the naked eye.

Where should you look? If you can find Venus, you can find the comet. Look low and southeast before sunrise. Comet Erasmus is in the constellation Hydra just to the right of Venus in neighboring Virgo. The bright star Spica is nearby, too, providing another useful reference point. Sky maps: Nov. 22, 23, 24, 25, 26.

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