Polar Mesospheric Summer Echoes

May 21, 2019: Every summer since the late 1970s, radars probing Earth’s upper atmosphere have detected strong echoes from altitudes between 80 km and 90 km. What’s up there? Noctilucent clouds (NLCs). NASA’s AIM spacecraft is still waiting to spot the first NLCs of the 2019 season, but the echoes have already begun. Rob Stammes of the Polarlightcenter in Lofoten, Norway, detected them on May 19th and 20th:


“I detected these VHF signals coming from transmitters in Eastern Europe,” he explains. “Before they reached my receiver in Norway, they bounced off something in the mesosphere. The patterns were recognizable and very strong.”

Researchers call them “Polar Mesospheric Summer Echoes” or “PMSEs.” They occur over the Arctic during the months of May through August, and over the Antarctic during the months of November through February. These are the same months that NLCs appear.

The underlying physics of these echoes is still uncertain. A leading theory holds that the ice particles in noctilucent clouds are electrically charged, and this makes them good reflectors of radio waves. However, NLCs are not always visible when the radar echoes are observed and vice versa.


Noctilucent clouds observed by Kairo Kiitsak of Simuna, Estonia, on on July 26, 2018.

The echoes Stammes detected suggest that the season for NLCs is about to begin.

“It certainly should be starting soon!” says Cora Randall of the AIM science team at the University of Colorado. “We’ve been looking at MLS temperature and water vapor data. As of last week, the north polar mesopause was colder and wetter than in any other years of the AIM record at this time.” In other words, conditions are ripe for water vapor to crystallize around meteor smoke, forming icy tendrils of electric-blue at the edge of space.

High-latitude sky watchers should be alert for their return. Observing tips: Look west 30 to 60 minutes after sunset when the sun has dipped 6o to 16o below the horizon. If you see luminous blue-white tendrils spreading across the sky, you may have spotted a noctilucent cloud.

Realtime Noctilucent Cloud Photo Gallery


Is the Great Red Spot Unraveling?

May 20, 2019: Around the world, amateur astronomers are monitoring a strange phenomenon on the verge of Jupiter’s Great Red Spot (GRS). The giant storm appears to be unraveling. “I haven’t seen this before in my 17-or-so years of imaging Jupiter,” reports veteran observer Anthony Wesley of Australia, who photographed a streamer of gas detaching itself from the GRS on May 19th:


The plume of gas is enormous, stretching more than 10,000 km from the central storm to a nearby jet stream that appears to be carrying it away. Wesley says that such a streamer is peeling off every week or so.

The Great Red Spot is the biggest storm in the solar system–an anticyclone wider than Earth with winds blowing 350 mph. Astronomers have been observing it for hundreds of years. In recent decades, the Great Red Spot has been shrinking. Once it was wide enough to swallow three Earths; now only one of our planet could fit inside the maelstrom. This has led some researchers to wonder if the GRS could break up or disappear within our lifetimes. Perhaps the streamers are part of this process.

In fact, such unraveling clouds have been seen before. For instance, the Gemini North adaptive optics telescope on Maunakea saw a lesser but similar streamer in May of 2017:


The leader of those observations, Glenn Orton of NASA’s Jet Propulsion Laboratory, noted “a curious hook-like cloud feature on the Great Red Spot’s western side. Events like this show that there’s still much to learn about Jupiter’s atmosphere,” he said in a press release.

Wesley describes how the streamers are behaving now: “Each streamer appears to disconnect from the Great Red Spot and dissipate. Then, after about a week, a new streamer forms and the process repeats. You have to be lucky to catch it happening. Jupiter spins on its axis every 10 hours and the GRS is not always visible. A joint effort between many amateurs is underway to get clear images of the process.”

Indeed, now is a great time to monitor the action. Jupiter is approaching Earth for a close encounter in June 2019. During the weeks around opposition on June 10th, Jupiter will shine 4 times brighter than Sirius, the brightest star in the sky, and even small telescopes will reveal its storms, moons, and cloud belts.

Stay tuned for more unraveling.

A Series of CMEs Approaches Earth

May 13, 2019: Three and possibly four CMEs are en route to Earth following a series of explosions near sunspot AR2741. The most potent so far occurred on May 12th when a filament of magnetism surrounding the sunspot became unstable and erupted. The blast zone was more than 220,000 km in diameter:

Similar eruptions on May 10th, 11th and 13th combined with this one to produce a train of faint coronal mass ejections (CMEs) heading in our direction. The incoming CMEs are lightweights compared to the bright massive CMEs typically seen during Solar Maximum. However, their combined effect could rattle Earth’s magnetic field.

NOAA forecasters estimate a 55% to 60% chance of G1-class geomagnetic storms on May 15th and 16th. Isolated periods of even stronger G2-class storms are possible as well. Aurora Alerts: SMS Text.

Realtime Aurora Photo Gallery

Rare Blue Auroras over Canada

May 11, 2019: Northern Lights are usually green, sometimes red. Those are the colors we see when oxygen is hit by electrons raining down from space during a geomagnetic storm. On Friday night, however, Harlan Thomas of Calgary, Alberta, witnessed a different color: deep-blue.

“To see these incredible blue pillars was out of this world,” says Thomas.

In auroras, blue is a sign of nitrogen. Energetic particles striking ionized molecular nitrogen (N2+) at very high altitudes can produce a blue glow rarely seen during auroral displays. In this case, it was the afterglow of a CME impact.

The CME left the sun on May 6th, propelled in our direction by an explosion in the magnetic canopy of sunspot AR2740. When it finally arrived on May 10th, the slow-moving storm cloud rattled Earth’s magnetic field, triggering a minor G1-class geomagnetic storm. Auroras were sighted in parts of Canada as well as US States such as Michigan and Minnesota.

“To top it off, STEVE appeared for several minutes as well,” says Thomas, who captured it in this shot:

STEVE is a hot (3000 degrees C) ribbon of ionized gas slicing through Earth’s upper atmosphere some 300 km above the ground. It appears unpredictably during some, but not all, geomagnetic storms. Originally thought to be a form of aurora borealis, new research shows that it is not an aurora at all.

The soft purple color of STEVE may also be caused by emissions from nitrogen, according to a new study just published in the Geophysical Research Letters. Coincidence? STEVE and blue auroras seem to share a connection to the 7th element on the periodic table.

Blue auroras are most often seen during intense geomagnetic storms–yet this was a relatively minor storm. Why nitrogen-blue overtopped the usual hues of oxygen on May 11th is unclear. It just goes to show, auroras still have the capacity to surprise. Aurora Alerts: SMS Text.

Realtime Aurora Photo Gallery

What is a Geomagnetic Jerk?

May 2, 2019: Earth’s magnetic field is notoriously inconstant. The north pole itself has been wandering across the Arctic for centuries. Currently, it is racing from northern Canada toward Siberia on an unpredictable path that has prompted hurried updates to world magnetic models. And then there are the “geomagnetic jerks.” Every 3 to 12 years, Earth’s magnetic field suddenly accelerates in one direction or another, a phenomenon that has puzzled scientists since it was recognized in the late 1970s.

Above: The rate of change in vertical magnetic fields at the Honolulu observatory (blue) and in Earth’s orbit (red). Sudden changes in the slope indicate geomagnetic jerks. [More]

The most recent jerk occurred in 2017 following a rapid-fire sequence of similar disturbances in 2008, 2011, and 2014. There is evidence for jerks going all the way back to 1901. Some are global, felt everywhere, while others are regional, spanning single continents or less. The unpredictability of jerks has complicated efforts to forecast geomagnetism.

A new study may solve the mystery. In a paper published on April 22nd in Nature Geoscience, Julien Aubert (Paris Institute of Earth Physics) and Christopher C. Finlay (Technical University of Denmark), describe how they created a computer model for geomagnetic jerks based on the physics of hydrodynamic waves in Earth’s molten core. According to their model, jerks originate in rising blobs of metal that form deep inside our planet. These slow-moving blobs can take 25 years to rise to the top of the convection zone. As they buoy upwards, the blobs disrupt the normal flow of magnetic field-generating currents and, in turn, cause jerks. The model successfully reproduces the form and timing of recent events.

Above: A computer simulation of molten blobs floating up from Earth’s core. Credit: Aubert and Finlay, Nature Geoscience (2018)

Geomagnetic jerks are just one aspect of Earth’s magnetic variability. Globally, Earth’s magnetic field has weakened by more than 10% since the 19th century with an even faster decline in the 2000s. Satellite data show the changes are uneven. According to CHAMP, Ørsted, and SWARM, the field has recently weakened by about 3.5% at high latitudes over North America, while it has strengthened about 2% over Asia. The region where the field is at its weakest – the South Atlantic Anomaly – has moved steadily westward and weakened further by about 2%.

At present, no one can predict these changes. However, Aubert and Finley’s successful model of jerks suggests that a deeper understanding may be within reach. You can read their original research here.

Note: The name “jerk” was borrowed from dynamics, where it means the rate of change of the acceleration of a body–that is, the third derivative of its position with respect to time. Geomagnetic jerks are therefore the first derivative of magnetic acceleration.

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Naked Eye Sprite Storms

April 30, 2019: Have you ever seen a sprite? Some say it’s impossible. The strange and fleeting forms of red lightning materialize above thunderheads, then disappear again in less time than it takes to blink. Yet this week veteran sprite chaser Paul Smith says he did see them: “I’ve watched a number with my bare eyes over the last two big storms in Kansas.”

Above: Naked-eye sprites over Kansas on April 28th. Credit: Paul Smith.

“It has been an amazing experience that, quite honestly, has left me somewhat emotional,” says Smith. “I am now convinced that before the days of light pollution, these were observed more often than we know.”

Sprites are an exotic form of electricity that leap up from storm clouds instead of down like ordinary lightning. Although sprites have been reported for at least a century, many scientists did not believe they existed until after 1989 when sprites were accidentally photographed by researchers from the University of Minnesota and confirmed by video cameras onboard the space shuttle.

Smith has been chasing and photographing sprites for years in the stormy Great Plains around Oklahoma and Kansas. “This is the first time I have seen them with my unaided eyes,” he says. “I believe that these were unusually bright.” Here are two examples of clusters he caught simultaneously with his eyes and camera.

His eyes registered fewer details than his camera–but he still saw plenty. “The jellyfish shapes I saw had a fiery orange/red color,” he adds. “I didn’t see the bottoms of the tendrils, but I had an impression of the heads and beads. Storm chasers to the west of me were also viewing with their naked eyes.”

The underlying physics of sprites is still not fully understood. Some models hold that cosmic rays help them get started by creating conductive paths in the atmosphere. If cosmic rays do indeed spark sprites, now is a good time to look for them because cosmic rays are nearing a Space Age high.

More examples of naked-eye sprites may be found on Smith’s Facebook page.

A Perfect Storm of Cosmic Rays

April 23, 2019: Ten years ago, NASA reported a “perfect storm of cosmic rays.” During the year 2009, radiation peppering Earth from deep space reached a 50-year high, registering levels never before seen during the Space Age.

It’s about to happen again.

Ground-based neutron monitors and high-altitude cosmic ray balloons are registering a new increase in cosmic rays. The Oulu neutron monitor in Finland, which has been making measurements since 1964, reports levels in April 2019 only percentage points below the Space Age maximum of 2009:


Source: The Sodankyla Geophysical Observatory in Oulu, Finland.

What’s going on? The answer is “Solar Minimum.” During the low phase of the 11-year solar cycle, the sun’s magnetic field and solar wind weaken. Cosmic rays find it easier to penetrate the inner solar system. In 2009, the sun experienced the deepest solar minimum in a century. Cosmic rays reaching Earth naturally surged.

Ten years later, solar minimum is back with renewed weakening of the sun’s magnetic field and the solar wind. Again, it’s a “perfect storm.” A panel of experts led by NOAA and NASA recently predicted that the current minimum would reach a nadir in late 2019 or 2020, likely matching the record-setting minimum of 2009. If they’re right, cosmic rays will continue to increase, with a new record possible in the near future.


Four years of overlapping data from neutron monitors and cosmic ray balloons agree that atmospheric radiation is increasing again.

Cosmic rays cause “air showers” of secondary particles when they hit Earth’s atmosphere. Indeed, this is what neutron monitors and cosmic ray balloons are measuring–the secondary spray of cosmic rays that rains down on Earth.

This spray is of special interest to air travelers. Secondary cosmic rays penetrate the hulls of commercial aircraft, dosing passengers with the whole body equivalent of a dental X-ray even on ordinary mid-latitude flights across the USA. International travelers receive even greater doses.

The International Commission on Radiological Protection has classified pilots as occupational radiation workers because of accumulated cosmic ray doses they receive while flying. Moreover, a recent study by researchers at the Harvard School of Public Health shows that flight attendants face an elevated risk of cancer compared to members of the general population. They listed cosmic rays as one of several risk factors.

Stay tuned for updates as solar minimum deepens.

Neutron Radiation over the USA

April 17, 2019: Want to experience space weather? Just step onboard an airplane. At typical cruising altitudes, cosmic rays from deep space penetrate the hulls of commercial jetliners, dosing passengers with levels of radiation comparable to dental X-rays. To measure this radiation, Spaceweather.com and the students of Earth to Sky Calculus have been flying cosmic ray sensors onboard airplanes over 5 continents. Our latest results show something potentially interesting about the continental USA.

Above: Neutrons detected during a flight from Portland to DC on April 9,2019.

On April 9th and 11th we flew neutron bubble chambers from Portland, Oregon, to Washington DC and back again. In the photo, above, each bubble was created by a cosmic ray neutron. Why measure neutrons? Studies show that neutrons can be ten times more effective at causing biological damage compared to X-rays and gamma-rays in the same energy range. Neutrons are so effective, they are used for cancer therapy, killing tumors better than other forms of radiation.

During these flights, we measured more than 20 uGy of neutron radiation–the whole body equivalent of two panoramic dental X-rays. That’s significant, but no worse than a trip to the dentist’s office.

The interesting thing is how these values compare to other places we’ve flown. Our neutron chambers have traveled more than 40,000 miles on 14 flights over North America, South America, Asia, Europe, and Africa, all with typical altitudes near 35,000 feet. So far, neutron dose rates have been highest in one place: the continental USA (CONUS).

In this histogram, flights over CONUS are color-coded red. Other parts of the world are blue. The distribution’s red tail shows the tendency of US flights to “out-neutron” international flights. This may be a result of small-number statistics. If so, the anomaly could disappear as more data are added. Our neutron survey is continuing, so stay tuned.

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Big Sunspot Produces “Ocean Surf” Sounds

April 15, 2019: If you have a shortwave radio, you might have heard some unusual sounds this weekend. Big sunspot AR2738 is producing strong bursts of radio static. “They sound like ocean surf,” says Thomas Ashcraft, who recorded this specimen on April 13th using an amateur radio telescope in New Mexico:

These radio sounds are caused by beams of electrons–in this case, accelerated by B-class explosions in the sunspot’s magnetic canopy. As the electrons slice through the sun’s atmosphere, they generate a ripple of plasma waves and radio emissions detectable on Earth 93 million miles away. Astronomers classify solar radio bursts into five types; Ashcraft’s recording captured a Type III.

“There have been a lot of these sounds over the past week, and they appear to be intensifying now that the sunspot is  directly facing Earth,” says Ashcraft.

Readers, if you would like to detect solar radio bursts in your own backyard, order a radio telescope kit from NASA’s RadioJOVE project.

Realtime Space Weather Photo Gallery

MOTHER’S DAY IS LESS THAN ONE MONTH AWAY: Tell Mom how much you love her — to the Moon and Back! On March 5th, the students of Earth to Sky Calculus launched an array of cosmic ray sensors to the edge of space onboard a helium balloon. This Mother’s Day pendant went along for the ride:

The silvery crescent declares “I love you to the Moon and Back” and surrounds a 14K gold plated heart labeled “Mom.”

You can have it for $99.95. The students are selling these pendants to support their cosmic ray ballooning program. Each one comes with a greeting card showing the item in flight and telling the story of its journey to the edge of space. Sales support the Earth to Sky Calculus cosmic ray ballooning program and hands-on STEM research.

Far Out Gifts: Earth to Sky Store
All sales support hands-on STEM education

Experts Predict a Long, Deep Solar Minimum

April 10, 2019:  If you like solar minimum, good news: It could last for years. That was one of the predictions issued last week by an international panel of experts who gathered at NOAA’s annual Space Weather Workshop to forecast the next solar cycle. If the panel is correct, already-low sunspot counts will reach a nadir sometime between July 2019 and Sept 2020, followed by a slow recovery toward a new Solar Maximum in 2023-2026.

“We expect Solar Cycle 25 will be very similar to Cycle 24: another fairly weak maximum, preceded by a long, deep minimum,” says panel co-chair Lisa Upton, a solar physicist with Space Systems Research Corp.


The solar cycle is like a pendulum, swinging back and forth between periods of high and low sunspot number every 11 years or so. Researchers have been tracking the cycle since it was discovered in the 19th century. Not all cycles are alike. Some are intense, with lots of sunspots and explosive solar flares; the Space Age began with a big booming solar maximum. Others are weak, such as the most recent, Solar Cycle 24, which peaked in 2012-2014 with relatively little action.

Researchers are still learning to predict the ebb and flow of solar activity. Forecasting techniques range from physical models of the sun’s inner magnetic dynamo to statistical methods akin to those used by stock market analysts.

“We assessed ~61 predictions in the following categories: Climatology, Dynamo, Machine Learning/Neural Networks, Precursor Methods, Spectral/Statistical Methods, Surface Flux Transport, and Other,” says Upton. “The majority agreed that Solar Cycle 25 would be very similar to Solar Cycle 24.”

“Here,” she says, “is a figure showing the last minimum and where we are with the current minimum.”


“As you can see – we haven’t quite reached the lowest levels of the last cycle – where we experienced several consecutive months with no sunspots. However, the panel expects that we should reach those levels [between now and the end of 2020].”

In recent years, the Internet has buzzed with the idea that a super-deep solar minimum such as the 70-year Maunder Minimum of the 17th century might cool the Earth, saving us from climate change. That’s not what the panel is saying, however.

“There is no indication that we are currently approaching a Maunder-type minimum in solar activity,” says Upton. Solar minimum will be deep, but not that deep.

The panel predicts a “fairly weak” Solar Cycle 25. What does that mean? Saying that a solar cycle is “weak” is a bit like saying hurricane season will be “weak.” In other words, there may be fewer storms, but when a storm comes, you’d better batten down the hatches. “Weak” Solar Cycle 24 produced a number of intense X-class solar flares, strong geomagnetic storms, and even a Ground Level Event (GLE) when solar energetic particles reached Earth’s surface. An equally “weak” Solar Cycle 25 could do the same 3 or 4 years hence.


Meanwhile, we have solar minimum. This is a widely misunderstood phase of the solar cycle. Many people think it brings a period of dull quiet. In fact, space weather changes in interesting ways. For instance, as the sun’s magnetic field weakens, holes open in the sun’s atmosphere. Emerging streams of solar wind buffet Earth’s magnetic field, sustaining auroras even without solar flares and sunspots. Some observers believe that Solar Minimum auroras have a distinctive palette, pinker than during other phases of the solar cycle.

The sun’s weakening magnetic field also allows cosmic rays to enter the solar system. Energetic particles from deep space penetrate Earth’s atmosphere with a myriad of possible effects ranging from changes in upper atmospheric electricity to extra doses of radiation for people on airplanes.

Finally, the sun dims, especially at extreme ultraviolet wavelengths. This, in turn, causes the upper atmosphere to cool and contract. Aerodynamic drag that would normally cause satellites to decay is reduced; space junk accumulates. This effect makes solar minimum a terrible time to blow up satellites–although people do it anyway.

The Solar Cycle Prediction Panel is comprised of scientists representing NOAA, NASA, the International Space Environment Services, and other U.S. and international scientists. Their April 5th prediction was preliminary, and they plan to issue a refined forecast by the end of 2019. Stay tuned.