Reflected Tsunamis and Space Weather

April 28, 2020: When the Earth trembles, even the edge of space moves. Researchers  have known for decades that earthquakes and tsunamis send waves of air pressure to the very top of Earth’s atmosphere. Up there, in the ionosphere, the waves scramble GPS signals and interfere with radio communications much like solar flares do. Earthquakes, it turns out, can mimic space weather.

A new paper published in the research journal Space Weather shows that earthquakes and tsunamis may, in fact, affect the ionosphere much more than previously thought.

“On 11 March 2011, a magnitude 9.0 earthquake occurred near the east coast of Honshu, Japan, unleashing a savage tsunami as well as unprecedented ripples at the space‐atmosphere interaction region,” report the authors, led by Min-Yang Chou of the University Corporation for Atmospheric Research (UCAR) in Boulder, CO.

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Above: Ionospheric disturbances over Japan caused by the March 11, 2011, earthquake and tsunami. The colors denote total electron content (TEC) measurements from ground-based global positioning receivers. This is Figure 6 from “The Persistent Ionospheric Responses Over Japan After the Impact of the 2011 Tohoku Earthquake,” by Min-Yang Chou.

Using satellites and ground-based GPS receivers, Chou and colleagues took a close look at what happened to the ionosphere over Japan in the aftermath of the earthquake. As expected, it was disturbed. Surprisingly, though, the ionospheric disturbances didn’t peter out after the initial quake and tsunami; they kept going for many more hours.

The reason: Reflected tsunamis.

“The tsunami was reflected by multiple sources such as seamounts, islands and ridges,” says Chou. “These reflections created multiple concentric tsunami wave patterns in the ocean.” Bouncing back and forth across the Pacific, reflected tsunamis kept the ionosphere above Japan disturbed for as much as 46 hours.

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Reflected tsunami waves backscattered by (a-c) seafloor topography on 11 March 2011 and backscattered by (d) South America on 13 March 2011. From the models of Tang et al. (2012)

Researchers once thought that only the sun could disturb the ionosphere so much. Solar flares bathe the top of our atmosphere with ultraviolet and X-radiation, sending waves of ionization rippling through the ionosphere. Sound familiar? Earthquakes and tsunamis have the same effect. In fact, Chou says, the disturbances over Japan were akin to a series of strong X-class solar flares.

In some ways, tsunamis are even worse. The disturbances they produce last for days and, because of reflections, can be very complicated. Reflected waves near Japan in 2011 caused chaotic nighttime “twinkling” of GPS satellite signals–enough to cause some GPS devices to completely lose lock.

As 2020 unfolds, the sun is experiencing one of the deepest Solar Minima of the past century. There are no solar flares. At a time like this, earthquakes and tsunamis rule, mimicking stormy space weather in the absence of the real thing.

Now more than ever, “understanding how natural hazards [such as tsunamis] impact our upper atmosphere and cause variations in the space environment around Earth is crucial,” says Chou.

For more information, read the original research here.

Severe Spring Storms Send Sprite-Lightning to the Edge of Space

April 23, 2020: A series of unusually severe spring storms parading across the southeastern USA has residents taking shelter from golf-ball sized hail and dangerous tornadoes. High above the maelstrom, sprites are dancing. Paul M. Smith of Edmond, Oklahoma, captured these specimens on April 22nd.

“There were tornado warnings and very large hail throughout the night,” says Smith. “I photographed the sprites through a clearing around midnight.”

Sprites are a form of electricity in powerful storm clouds. While regular lightning lances down, sprites leap up. They can reach all the way to the edge of space 90 km or more above Earth’s surface. Spring thunderstorms often produce the year’s first big sprites, and the sightings continue through late summer.

“My camera was pointed toward Oklahoma City,” says Smith, “and the sprites were about 150 miles away.” This radar weather map shows shows the observing geometry:

When observing sprites, this kind of distance is a good thing. It allows a camera to see over the top of the thunderhead into the sprite zone. It also provides a measure of safety, separating the photographer from lightning strikes.

Smith also photographed sprites on Easter Sunday. They towered over a storm in Arkansas that made headlines for its ferocity and destructiveness. “The sprites were so bright, I was able to photograph them in almost-full moonlight,” he says.

This could turn into one of the best sprite seasons on record. Why? Solar Minimum. The sun is currently experiencing one of the deepest minima in 100 years. As the sun’s magnetic field weakens, more cosmic rays from deep space are reaching Earth. Some researchers believe that cosmic rays help sprites get started by creating conductive paths in the atmosphere. Intensifying cosmic rays could produce an unusually spriteful spring.

Are you ready?

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Astronauts Photograph Starlink Satellites from Space

April 20, 2020: For the first time, SpaceX’s controversial Starlink satellites have been photographed by astronauts onboard the International Space Station. Here they are, photo-bombing a display of aurora australis on April 13, 2020:

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The ISS was flying over the southern Indian Ocean when the sighting occurred with cameras pointing generally south toward Antarctica. At the time, a minor stream of solar wind was buffeting Earth’s magnetic field, sparking auroras over the frozen continent. The Starlink train stretches all the way from the twilight-blue horizon to the starry sky high above the aurora layer.

Dutch satellite expert Marco Langbroek identified the Starlink satellites and labeled the original NASA image. “These are all objects from the 17 February 2020 launch— a.k.a. ‘Starlink 4,'” Langbroek wrote in his blog.

Starlink is a new venture by SpaceX, which aims to surround Earth with satellites and beam affordable internet to remote locations all over the world. It is controversial because of its potential effect on the night sky. Just after launch, Starlink satellites easily can be seen with the unaided eye, swarming across stars and planets familiar to backyard astronomers. Scott Tucker of Tucson, Arizona, was photographing Venus on the evening of April 17th when this happened:

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“I watched 41 Starlink satellites from the most recent launch pass by Venus during late twilight,” says Tucker. “One of them even flared like an Iridium satellite! It got to magnitude -2 for a few seconds.”

Newly-launched Starlink satellites eventually dim as they approach operational orbits 550 km above Earth–but even then they can interfere with research astronomy. Big telescopes have no trouble detecting Starlink satellites no matter how high they go. The fact that SpaceX plans to launch at least 12,000 of them has prompted the International Astronomical Union to sound the alarm.

So far, there are 360 Starlinks into Earth orbit, a tiny fraction of the ultimate total, yet still a large number. Accidental sightings have become so common that we now have an entire photo gallery of Starlink sightings. Browse the collection and see what you think.

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Introducing Comet SWAN

April 15, 2020: Warning: This story may give you a sense of déjà vu. A new comet has been discovered, and in late May it will pass by the sun near the orbit of Mercury. No, it’s not Comet ATLAS (C/2019 Y4), which is currently falling apart on a similar trajectory. Instead, this is Comet SWAN (C/2020 F8):

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Michael Mattiazzo of Swan Hill, Victoria, Australia, took the picture on April 13th. “This is a 5 minute exposure through my 11-inch Celestron telescope,” says Mattiazzo. “A visual observation using 15x70mm binoculars gave a magnitude of 8.1.”

Mattiazzo discovered the comet two days earlier when he was looking at data from the Solar and Heliospheric Observatory (SOHO). It suddenly appeared in images from SOHO’s SWAN instrument. “This is my 8th discovery credit for SWAN comets since 2004 and I do check the data on most days,” says Mattiazzo.

Post-discovery images taken by Italian astronomer Ernest Guido and colleagues confirm that the comet is bright (8th magnitude), green, and has a long tail:

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“We took this picture on April 11th–the same day Mattiazzo found the comet in SWAN data,” says Guido. “We couldn’t see it from Italy, so we used a remote-controlled 0.1 meter telescope in Australia.”

SOHO’s SWAN instrument was not designed to find comets. Its job is to survey the solar system for hydrogen. When the solar wind blows into a cloud of hydrogen-bearing compounds, the impact produces UV photons that SWAN can photograph.

“For SWAN to see a comet, it means the comet must be producing a fairly significant amount of hydrogen,” explains Karl Battams of the Naval Research Lab in Washington DC. “This is usually in the form of water-ice.”

“It’s extremely likely that Comet SWAN is in ‘outburst’ mode,” he continues. “That is, some major eruption happened to this otherwise small and faint comet, releasing a massive cloud of hydrogen-rich volatiles. SWAN is picking up on this sudden dump of hydrogen into the inner solar system.”

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Click to view an interactive preliminary orbit of Comet SWAN. Credit: Gideon van Buitenen

If the outburst continues, Comet SWAN could become visible to the naked eye next month. Preliminary light curves suggest that it could reach 3rd magnitude–dim, but visible without optics. However, Battams, who correctly predicted the demise of Comet ATLAS, is not so sure.

“I doubt that the comet will maintain its current impressive appearance, and will quite possibly fade away soon,” he says. “But we’ve only been viewing it for a couple of days, so no one knows.”

Comet SWAN is currently located in southern skies, best seen by telescopes in Australia, New Zealand, southern Africa and South America. Preliminary orbital elements are available here. Stay tuned for updates.

Fragments of Comet ATLAS

April 13, 2020: There’s no longer any doubt. Comet ATLAS (C/2019 Y4) is falling apart. Around the world, amateur astronomers are beginning to witness the breakup, even imaging individual fragments. Jose de Queiroz photographed 3 pieces on April 11th:

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“I took the picture using the 90 cm telescope at Observatory Mirasteilas in Falera, Switzerland,” says de Queiroz. “This is a stacked 20×120 sec exposure.”

Confirming images from the Lulin One-meter Telescope in Taiwan have just been reported in an Astronomer’s Telegram. The observing team, led by Zhong-Yi Lin of Taiwan’s National Central University, estimates that the leading fragment is about 3400 km ahead of the trailing pair.

The breakup of Comet ATLAS coincides with a sharp decline in its brightness. The Comet Observation Database shows a drop of two full magnitudes (a factor of more than 6):

lightcurve

These trends suggest that the comet *might* completely dissolve before its close approach to the sun inside the orbit of Mercury at the end of May. “Follow-up observations of C/2019 Y4 (ATLAS), both imaging and spectroscopy, are highly recommended to investigate the cause of this cometary breakup event,” says Lin and colleagues.

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Where the Power Might Go Out

April 9, 2020: A solar superstorm can make your lights go out. New maps released by the USGS show where the power is most likely to fail: The Denver metropolitan area, the Pacific northwest, the Atlantic seaboard, and a cluster of Midwestern states near the US-Canadian Border. Bright yellow and orange trace the trouble spots across the contiguous USA:

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Power companies have long been wary of the sun. Solar storms can cause strong electric currents to flow through commercial power lines–so strong that the lines can’t handle it. Fuses blow, transformers melt, and circuit breakers trip. The most famous geomagnetic power outage happened during a space storm in March 1989 when six million people in Quebec lost power for 9 hours.

Whether or not *your* power goes out during a solar storm depends on two things: (1) The configuration of power lines in your area and (2) the electrical properties of the ground beneath your feet. In areas of more electrically resistive rock, currents struggle to flow through the ground. Instead, they leap up into overhead power lines – a scenario that played out in Quebec in 1989.

The new maps are possible thanks to Earthscope–a National Science Foundation magnetotelluric survey of the upper 2/3rds of the contiguous USA. Earthscope mapped the electrical properties of deep rock and soil on a continent-spanning grid with points about 70 km apart. USGS researchers led by Greg Lucas and Jeffrey Love combined this information with the layout of modern power lines to estimate peak voltages during a century-class storm.

Electric powerlines

Sprawling power lines act like “solar storm antennas,” picking up currents and spreading the problem over a wide area.

They found a huge variation in hazard across the USA. “The largest estimated once-per-century geoelectric field is 27.2 V/km at a site located in Maine, while the lowest estimated once-per-century geoelectric field is 0.02 V/km at a site located in Idaho. That is more than 3 orders of magnitude difference,” they wrote in their research paper “A 100‐year Geoelectric Hazard Analysis for the U.S. High‐Voltage Power Grid.” Notably, some of the most vulnerable regions are near big cities: Denver, Boston, New York, Philadelphia, Baltimore, and Washington, DC.

To complete the hazard map, the researchers are waiting for a new magnetotelluric survey to cover the rest of the USA. It can’t come soon enough. The last “century-class” geomagnetic storm hit in May 1921 … 99 years ago.

Comet ATLAS is Breaking Up

April 6, 2020: Comet ATLAS (C/2019 Y4), what are you doing? New data from astronomers around the world show that the once-promising comet is beginning to fade. For Karl Battams of the Naval Research Lab in Washington DC, it could be a classic case of “I told you so.”

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Comet ATLAS on March 28th. Credit: Tim Connolly of Plattsburgh, NY. [More images]

“Quoting myself from March 15th,” says Battams, “‘I wouldn’t be surprised to see Comet ATLAS start to fade rapidly and possibly even disintegrate before reaching the sun.’ I very much hope I’m wrong, but Comet Elenin did something similar several years ago, holding lots of promise and then just… fizzling.”

In recent months, Comet ATLAS galvanized astronomers as it fell toward the sun, skyrocketing in brightness like few comets before it. By late May 2020 it promised to rival Venus in the sunset sky. But recent developments belie that possibility.

On April 6th, astronomers Quanzhi Ye of the University of Maryland) and Qicheng Zhang of Caltech reported new images of Comet ATLAS, in which the comet’s core appears to be elongating–“as would be expected from a major disruption of the nucleus,” they wrote in an Astronomical Telegram.

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Images from the 0.6-m Ningbo Education Xinjiang Telescope show a possible fragmentation of ATLAS’s core

“It’s possible that this is the beginning of the end,” says Battams.

Recent measurements of the comet’s position also point to trouble. Battams explains: “The comet’s orbit is now being influenced by ‘non-gravitational’ forces. These forces are the result of gases lifting off the comet nucleus and causing the nucleus to move very slightly in the opposite direction–sort of like a jet engine. Most active comets experience this to some degree, but ATLAS’s non-gravitational forces have kicked in very abruptly and are quite strong. This supports a narrative of a small nucleus being pushed very strongly by extreme outgassing, possibly along with fragmentation.”

“Finally, let’s not forget that ATLAS is a fragment of a larger (unidentified) comet also related to the Great Comet of 1844,” says Battams. “Fragmenting is a family trait for these guys.”

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Is Comet ATLAS doomed? Not necessarily. “The frustrating thing about comets is we often don’t know exactly what they’re doing or why they’re doing it. There’s still a chance that Comet ATLAS is just ‘taking a breather’ before another outburst,” says Battams. “But I wouldn’t count on it….”

No matter what happens, amateur astronomers are encouraged to monitor developments. Submit your images here.

Noctilucent Clouds over the South Pacific

March 26, 2020: You don’t see this everyday–or even in 30 years. “Noctilucent clouds have appeared over the South Pacific,” reports  meteorologist Ashleigh Wilson of the Australian Antarctic Division. “I photographed them from Macquarie Island on Jan. 4th.”

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Noctilucent clouds over Macquarie Island on Jan. 4, 2020. Photo credit: Ashleigh Wilson of the Macquarie Island Bureau of Meteorology team, Australian Antarctic Division. [more]

Wilson is just wrapping up a year-long stint on the remote island where the Australian government maintains a research station to study climate change and wildlife. She’s been there, off and on, since the year 2000, and this is the first time she’s ever seen NLCs.

“According to John French of the Australian Antarctic Division Atmospheric Science Program, the only other photographic recording of NLCs on Macquarie Island was in the mid-1990s,” Wilson says.

NLCs are Earth’s highest clouds. Seeded by meteoroids, they float at the edge of space more than 80 km above the planet’s surface. NLCs form when summertime wisps of water vapor rise up to the edge of space and crystalize around specks of ‘meteor smoke.’ Prime time for sightings is June-July in the north, December-January in the south.

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“It was a breathtaking moment when I first realized what I was seeing,” recalls Wilson. “I had just finished my shift in the Met office at 11:30 pm and I was walking back to our dorms. Luminous filaments were crisscrossing the sky, blue in color with some wave formations. I spent two hours down by the ocean with a camera and tripod, adjusting ISO and lenses, trying to capture the extraordinary event. The clouds were so bright, I could see their reflection in the water.”

Wilson’s sighting caps a remarkable year for noctilucent clouds. Once confined to Earth’s polar regions, NLCs have recently spread to lower and lower latitudes. In 2019, the clouds appeared over Rome, Italy; Las Vegas, Nevada; Albuquerque, New Mexico; Paris, France; and outside Los Angeles, California. Many of the sightings smashed old records for low-latitude visibility.

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The recent spread of noctilucent clouds. The shaded area shows the traditional domain of NLCs. Black circles denote sightings during the northern summers of 2003-2011. Red circles are for June 2019. All data come from Spaceweather.com. The map originally appeared in JGR Atmospheres: article.

In the southern hemisphere, reports of *any* noctilucent clouds are quite rare–in part because there are fewer people on that side of the world; in part because southern NLCs are usually weaker than their northern counterparts. Nevertheless, NLCs were sighted over New Zealand in Dec. 2019 and Macquarie Island in Jan. 2020.

Why are NLCs so revved up? No one knows for sure. It could be a result of climate change and/or the solar cycle. Satellites have recently detected extra moisture in the mesosphere–a key ingredient of NLCs. That moisture may be surviving thanks to low solar activity. Right now a deep Solar Minimum is underway. Ultraviolet radiation that would normally destroy water in the mesosphere is at low ebb.

Get ready for more. The northern hemisphere season for NLCs is about to begin as summertime wisps of water vapor drift up toward the edge of space. The first electric-blue filaments are typically sighted in mid- to late-May. If recent events are any guide, 2020 could be very special indeed.

Stay tuned!

 

Comet ATLAS is Half as Wide as the Sun

March 24, 2020: No one knows how big the icy core of Comet ATLAS (C/2019 Y4) might be–possibly no wider than a few kilometers. One thing’s for sure, though, the comet’s atmosphere is huge. New images from amateur astronomers around the world show that ATLAS’s gaseous envelope has ballooned in diameter to ~720,000 km–about half as wide as the sun.

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“Comet ATLAS’s coma (atmosphere) is approximately 15 arcminutes in diameter,” reports Michael Jäger of Weißenkirchen, Austria, who took the picture, above, on March 18th. “Its newly-formed tail is about the same size.”

Other astronomers are getting similar results. 15 arcminutes = a quarter of a degree. Given Comet ATLAS’s distance of 1.1 AU on March 18th, that angle corresponds to a physical size of 720,000 km.

On the scale of big things in the solar system, Comet ATLAS falls somewhere between the sun (1,392,000 km  diameter) and Jupiter (139,820 km). It’s not unusual for comets to grow so large. While their icy solid cores are typically mere kilometers in diameter, they can spew prodigious amounts of gas and dust into space, filling enormous volumes. In the fall of 2007, Comet 17P/Holmes partially exploded and, for a while, had an atmosphere even larger than the sun. The Great Comet of 1811 also had a sun-sized coma. Whether Comet ATLAS will eventually rival those behemoths of the past remains to be seen.

Right now, Comet ATLAS is certainly the biggest green thing in the Solar System. Its verdant hue comes from diatomic carbon, C2, a molecule commonly found in comets.  Gaseous C2 emits a beautiful green glow in the near-vacuum of space.

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Currently, Comet ATLAS is shining like an 8th magnitude star–invisible to the unaided eye but an easy target for backyard telescopes. The comet is brightening rapidly as it comes closer to Earth and the sun. By late May it could rival Venus in the evening twilight sky. Stay tuned!

Comet ATLAS resources: sky map; 3D orbit; ephemeris, light curve.

Comet ATLAS is Brightening Faster than Expected

March 17, 2020: Get ready for a wild ride. Comet ATLAS (C2019 Y4) is plunging toward the sun, and if it doesn’t fly apart it could soon become one of the brightest comets in years.

“Comet ATLAS continues to brighten much faster than expected,” says Karl Battams of the Naval Research Lab in Washington DC. “Some predictions for its peak brightness now border on the absurd.”

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Above: Comet ATLAS (C/2019 Y4) photographed on March 6, 2020, by Austrian astrophotographer Michael Jäger. The comet’s diffuse green atmosphere is about twice as wide as the planet Jupiter.

The comet was discovered in December 2019 by the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Hawaii. Astronomers quickly realized it might be special. On May 31, 2020, Comet ATLAS will pass deep inside the orbit of Mercury only 0.25 AU from the sun. If it can survive the blast furnace of solar heating, it could put on a good show.

However, no one expected the show to start this soon. More than 2 months before perihelion (closest approach to the sun), Comet ATLAS is already “heating up.” The worldwide Comet Observation Database shows it jumping from magnitude +17 in early February to +8 in mid-March–a 4000-fold increase in brightness. It could become visible to the naked eye in early April.

“Right now the comet is releasing huge amounts of its frozen volatiles (gases),” says Battams. “That’s why it’s brightening so fast.”

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Can ATLAS sustain this crazy pace? If it has a big nucleus with large stores of frozen gas, then yes; we could get a very bright comet. Otherwise, Comet ATLAS might “run out of gas”, crumbling and fading as it approaches the sun.

Current best estimates of the comet’s peak brightness in May range from magnitude +1 to -5. If Comet ATLAS hits the high end of that range, a bit brighter than Venus, it could become visible in broad daylight.

Comet McNaught (C/2006 P1) performed that very trick 13 years ago. On Jan. 13, 2007, it swooped past the sun shining at magnitude -5. The absurdly-bright comet was visible at high noon with its tail jutting across blue sky.

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Above: Comet McNaught in broad daylight on Jan. 13, 2007. Photo credit: Peter Rosen
 of Stockholm, Sweden. [More]

Battams is not optimistic, though: “My personal intuition is that Comet ATLAS is over-achieving, and I wouldn’t be surprised to see it start to fade rapidly and possibly even disintegrate before reaching the sun,” he says.

Come to think of it, that would be a good show, too. Solar glare may challenge ground-based observers, but NASA has spacecraft with cameras that specialize in seeing things close to the sun.

“The Heliospheric Imager on NASA’s STEREO spacecraft will get a great view of ATLAS from mid-May through early June,” says Battams. “The camera is very sensitive, so we might be able to observe ATLAS’s tail interacting with the solar wind and outflows–as well as any potential breakup events.”

Stay tuned!