“Once in a Lifetime” Polar Stratospheric Clouds

Dec. 30, 2019: A spectacular outbreak of polar stratospheric clouds (PSCs) is underway around the Arctic Circle. “This is a once in a lifetime event,” says Chad Blakley, who runs the Lights over Lapland aurora tour service in Abisko, Sweden. “No question, this is the best that any of us have ever seen.” Tour guide Paige Ellis took this video showing the clouds’ aurora-like colors on Dec. 29th:


“They were so intense that lots of the tourists on the ground thought they were looking at daytime auroras. I had to explain that they were actually clouds in the stratosphere,” says Blakley.

Polar stratospheric clouds are newsworthy because normally the stratosphere has no clouds at all. Home to the ozone layer, the stratosphere is arid and almost always transparent. Only when the temperature drops to a staggeringly cold -85C can sparse water molecules assemble themselves into icy stratospheric clouds. PSCs are far more rare than auroras.

“Local villagers in both Abisko and Kiruna who are more than 70 years old confirmed they have never seen anything of the size, scale, or intensity,” reports Blakley. “At one point I would say that close to 25% of the sky was filled with the clouds. PSCs in previous winters have been closer to 1% or 2%.”

The outbreak has continued on Dec. 30th. “Today I got to see some of the brightest PSCs I’ve ever seen during all of my years watching the sky,” reports Göran Strand, who sends this picture from Jämtland, Sweden:

“They were so bright, they even lit up the surrounding landscape,” he marveled.

PSCs are intensely colorful because they are made of a special type of ice. High-altitude sunlight shining through microscopic crystals only ~10µm across produce a bright iridescent glow unlike the lesser iridescence of ordinary tropospheric clouds.

Stay tuned for updates as the outbreak continues.

Reversed Polarity Sunspots Appear on the Sun

Dec. 24, 2019: Solar Cycle 25 really is coming. Today, for the first time, there are two new-cycle sunspots on the solar disk–one in each hemisphere. This map of solar magnetic fields from NASA’s Solar Dynamics Observatory shows their location:

We know these sunspots belong to the next solar cycle because of their magnetic polarity. Simply put, they are backwards. According to Hale’s Law, sunspot polarities flip-flop from one solar cycle to the next. During old Solar Cycle 24, we grew accustomed to sunspots in the sun’s southern hemisphere having a -/+ pattern. However, look at today’s southern sunspot:

It is the opposite: +/-. This identifies it as a member of new Solar Cycle 25.

Likewise, today’s northern sunspot has a reversed polarity compared to northern spots from old Solar Cycle 24. It, too, therefore, belongs to Solar Cycle 25.

The sun is currently in Solar Minimum–the nadir of the 11-year sunspot cycle. It’s a deep Minimum, century-class according to sunspot counts. The scarcity of sunspots has been so remarkable that it has prompted discussion of a possible “extended Minimum” akin to the Maunder Minimum of the 17th century when sunspots were absent for decades. Such an event could have implications for terrestrial climate.

Today’s new-cycle sunspots (along with isolated new-cycle spots earlier this year) suggest that the solar cycle is, in fact, unfolding normally. A new Maunder Minimum does not appear to be in the offing. Forecasters expect Solar Cycle 25 to slowly gain strength in the years ahead and reach a peak in July 2025.

Sunspots set a Space Age Record

Dec. 17, 2019: Solar Minimum is becoming very deep indeed. Over the weekend, the sun set a Space Age record for spotlessness. So far in 2019, the sun has been without sunspots for more than 271 days, including the last 34 days in a row. Since the Space Age began, no other year has had this many blank suns.

Above: The blank sun on Dec. 16, 2019. Credit: NASA/Solar Dynamics Observatory

The previous record-holder was the year 2008, when the sun was blank for 268 days. That was during the epic Solar Minimum of 2008-2009, formerly the deepest of the Space Age. Now 2019 has moved into first place.

Solar Minimum is a normal part of the 11-year sunspot cycle. The past two (2008-2009 and 2018-2019) have been long and deep, making them “century-class” Minima. To find a year with more blank suns, you have to go back to 1913, which had 311 spotless days.

Last week, the NOAA/NASA Solar Cycle Prediction Panel issued a new forecast. Based on a variety of predictive techniques, they believe that the current Solar Minimum will reach its deepest point in April 2020 (+/- 6 months) followed by a new Solar Maximum in July 2025. This means that low sunspot counts and weak solar activity could continue for some time to come.

Solar Minimum definitely alters the character of space weather. Solar flares and geomagnetic storms subside, making it harder to catch Northern Lights at mid-latitudes. Space weather grows “quiet.” On the other hand, cosmic rays intensify. The sun’s weakening magnetic field allows more particles from deep space into the solar system, boosting radiation levels in Earth’s atmosphere. Indeed, this is happening now with atmospheric cosmic rays at a 5-year high and flirting with their own Space Age record. It’s something to think about the next time you step on an airplane.

Stay tuned for updates!

Cosmic Ray Update

Dec. 13, 2019: Something ironic is happening in Earth’s atmosphere. Solar activity is low–very low. Yet atmospheric radiation is heading in the opposite direction. Cosmic rays percolating through the air around us are at a 5 year high.

Take a look at these data gathered by cosmic ray balloons launched by Spaceweather.com and the students of Earth to Sky Calculus almost weekly since March 2015:


Radiation levels have been increasing almost non-stop since the monitoring program began, with recent flights registering the highest levels of all.

What’s happening? The answer is “Solar Minimum”–the low point of the 11-year solar cycle. During Solar Minimum (underway now) the sun’s magnetic field weakens and allows energetic particles from deep space to penetrate the Solar System. As solar activity goes down, cosmic rays go up; yin-yang.

When cosmic rays hit the top of Earth’s atmosphere, they produce a spray of secondary particles and photons that rain down on Earth’s surface. This is what our balloons measure–the secondary spray. We use X-ray and gamma-ray detectors sensitive to energies in the range 10 keV to 20 MeV. This type of radiation, which you can also find in medical X-ray machines and airport security scanners, has increased more than 20% in the stratosphere.


Another way to measure cosmic rays is using a neutron monitor. Neutrons are an important type of secondary cosmic ray. They reach Earth’s surface with relative ease and are biologically effective. Neutron monitors at the Sodankyla Geophysical Observatory in Oulu, Finland, are getting results similar to ours. Oulu data show that cosmic rays have been increasing for the past 5 years and, moreover, are within percentage points of the Space Age record.

The Space Age record for cosmic rays isn’t very old. It was was set in late 2009-early 2010 near the end of a very deep Solar Minimum much like the one we’re experiencing now. As 2019 comes to a close, neutron counts at Oulu are approaching those same levels. Indeed, a new record could be just weeks or months away.

Who cares? Anyone who steps on an airplane. Cosmic rays penetrate commercial jets, delivering whole-body dosages equal to one or more dental X-rays even on regular flights across the USA. Cosmic rays pose an even greater hazard to astronauts, of course. Cosmic rays can also alter the electro-chemistry of Earth’s upper atmosphere and are thought to play some role in sparking lightning.

Stay tuned for updates.

Planetary Wave Supercharges Southern Noctilucent Clouds

Dec. 4, 2019: An atmospheric wave nearly half as wide as Earth itself is supercharging noctilucent clouds (NLCs) in the southern hemisphere. NASA’s AIM spacecraft detected the phenomenon in this series of south polar images spanning Nov. 27th through Dec. 2nd:


“This is a clear sign of planetary wave activity,” says AIM principal investigator James Russell of Hampton University, which manages the Aeronomy of Ice in the Mesosphere mission for NASA.

Planetary waves are enormous ripples of temperature and pressure that form in Earth’s atmosphere in response to Coriolis forces. In this case, a 5-day planetary wave is boosting noctilucent clouds over Antarctica and causing them to spin outward to latitudes where NLCs are rarely seen.

On Dec. 1st, Mirko Harnisch saw the clouds from Dunedin, New Zealand. “I was enjoying the late-evening sky over the Southern Ocean just after 11 pm local time when these wispy blue-ish clouds appeared,” says Harnisch. “They looked like noctilucent clouds, which would make this a rare sighting for my latitude of 45S.”


Indeed, very rare. Spaceweather.com has been receiving images of NLCs for more than 20 years. This is the first-ever submission from New Zealand.

Noctilucent clouds over Antarctica itself are nothing unusual. They form every year around this time when the first wisps of summertime water vapor rise to the top of Earth’s atmosphere. Molecules of H2O adhere to specks of meteor smoke, forming ice crystals 83 km above Earth’s surface.

But these NLCs are different. They’re unusually strong and congregated in a coherent spinning mass.

“The planetary wave is responsible,” says AIM science team member Lynn Harvey of the University of Colorado’s Laboratory for Atmospheric and Space Physics (LASP). “It is concentrating a mass of cold water vapor in the mesosphere and causing it to pinwheel counterclockwise around the South Pole.”


Harvey has been tracking the moisture in data from NASA’s Microwave Limb Sounder instruments, shown above.  It matches almost perfectly the location of the NLCs.

Because the noctilucent clouds are spinning around with a 5 day period, they could return to New Zealand 5 days after Harnisch saw them–that is, on Dec. 6th. Such a forecast is very uncertain. Nevertheless, sky watchers who wish to try should look west 30 to 60 minutes after sunset. If you see luminous blue-white tendrils hugging the horizon, you may have spotted a noctilucent cloud.

A Possible Outburst of alpha Monocerotid Meteors

Nov. 20, 2019: Get ready for a meteor outburst–maybe. On Nov. 21-22, Earth will pass by a stream of dusty debris from an unknown comet. Forecasters Esko Lyytinen (Finnish Fireball Network) and Peter Jenniskens (NASA/Ames) believe this could cause an outburst of alpha Monocerotid meteors. Jenniskens witnessed a previous outburst in 1995:


“This is a composite of alpha Monocerotids detected in low-light video observations by Sirko Molau in Germany during the 1995 outburst,” says Jenniskens. “Most of the meteors ranged in magnitude from +2 to +0.”

No one knows exactly where alpha Monocerotid meteors come from. The parent comet has never been seen. Based on the dynamics of its debris, it probably circles the sun every 500 years or so. We know the comet exists only because of the narrow trail of dust it left behind long ago. Earth has run into the dust trail at least 4 times, causing bright outbursts of meteors in 1925, 1935, 1985 and 1995.

Lyytinen and Jenniskens recently realized that in 2019 Earth would pass about as close to the debris as it did in 1995–and so they issued this alert. The outburst is expected around 04:50 UT on Nov. 22nd (11:50 p.m. EST on Nov. 21st). Because the debris zone is narrow (only ~50,000 km wide), the outburst could last as little as 15 minutes and probably no more than 40 minutes, producing dozens of meteors during that short time.


People in western Europe may have the best view shortly before sunrise on Nov. 22nd. For them, the shower’s radiant in Monoceros (the Unicorn) will be relatively high in the southern sky. Sky watchers in eastern parts of North America can see the show, too, but not as well. As shown in the sky map, above, Monoceros will still be hugging the eastern horizon when the shower peaks over the east coast of Canada and the USA. West coast observers won’t be able to see Monoceros at all.

There’s no guarantee that anything will happen. Only a handful of alpha Monocerotid outbursts have been observed in the past century, which means researchers are still mapping the debris zone. Earth could hit a extra-dense spot, resulting in an amazing display, or pass through a void, producing nothing.

“We are crossing the dust trail along a different cord than in past returns and this will help understand how the dust is distributed perpendicular to the Earth’s path,” says Jenniskens. “Whatever happens, we are going to learn something.”

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Observing the Transit of Mercury

Nov. 10, 2019: What will tomorrow’s transit of Mercury look like? Marek Nikodem has the answer. He watched the previous transit of Mercury (May 9, 2016) from Kcynia, Poland, and photographed the event at sunset:

Mercury is the black dot near the bottom of the sun. It’s pretty tiny. Mercury is only 1/194th of the sun’s apparent diameter. That’s why looking at the sun through ordinary eclipse glasses won’t work. You need magnification–50x or more is recommended.

A safe way to view a magnified image of the sun is the projection method. This illustration from the European Space Agency says it all:

Any telescope with a stabilizing tripod can be used to project an image of the sun onto a wall, screen or sidewalk. It’s perfectly safe as long as you don’t look into the eyepiece. Binoculars work, too, with the same precautions.

Or, just stare at your computer screen! Transit of Mercury webcasts: (1) Royal Observatory Greenwich, UK on Facebook; (2) Timeanddate.com from Stavanger, Norway; (3) Griffiths Observatory TV from Los Angeles

Get Ready for the Transit of Mercury

Nov. 8, 2019: One of the biggest astronomy events of the year is only days away: The Transit on Mercury. On Monday, Nov 11th, Mercury will pass directly in front the sun. The rare transit begins at 12:35 UT (7:35 am EST) and lasts for almost six hours. Mercury’s tiny form—jet black and perfectly round—will glide slowly across the solar disk, like this:


Credit: Tom Polakis of Tempe AZ made this movie of a previous Mercury transit on May 9, 2016. [more]

People in every continent except Australia can see at least a portion of the crossing. In the USA, the best place to be is on the Atlantic coast, where the entire transit will be visible. On the Pacific coast the transit will already be in progress at sunrise.

Warning! Do not stare at the sun during the transit. Mercury covers only a tiny fraction of the solar disk, so the sun remains as bright as ever. Eye damage can occur.

Ordinary eclipse glasses will keep your eyes safe, but they won’t do much to help you see tiny Mercury. The planet is only 1/194th of the sun’s apparent diameter. To watch this event, a safely-filtered telescope with a magnification of 50x or more is recommended. Don’t have a filter? No problem. Images of the transit may be easily projected onto a wall or screen through an unfiltered telescope. Just do not look through the eye piece.

Nothing beats a telescope equipped with an H-alpha filter. H-alpha filters are narrowly tuned to the red glow of solar hydrogen. They reveal the sun as a boiling inferno cross-crossed by dark seething magnetic filaments. On Nov. 11th, the tiny form of Mercury will navigate this starscape. Here’s a sample H-alpha image taken during the last transit of Mercury on May 9, 2016:

Paul Andrew took the picture from his backyard observatory in St. Margarets at Cliffe, Dover, UK. “The background prominence made Mercury look like it had a comet’s tail,” he says. More images may be found here and here.

Transits of Mercury occur only 13 times each century. The next one won’t occur until Nov. 13, 2032. Don’t miss this unusual event!

Solar Cycle 25 is Slowly Coming to Life

Nov. 1, 2019: Breaking a string of 28 spotless days, a new sunspot (AR2750) is emerging in the sun’s southern hemisphere–and it’s a member of the next solar cycle. A picture of the sunspot is inset in this magnetic map of the sun’s surface from NASA’s Solar Dynamics Observatory:


How do we know AR2750 belongs to the next solar cycle? Its magnetic polarity tells us so. Southern sunspots from old Solar Cycle 24 have a -/+ polarity. This sunspot is the opposite: +/-. According to Hale’s Law, sunspots switch polarities from one solar cycle to the next. AR2750 is therefore a member of Solar Cycle 25.

Shortlived sunspots belonging to Solar Cycle 25 have already been reported on Dec. 20, 2016; April 8, 2018; Nov. 17, 2018; May 28, 2019; July 1, 2019; and July 8, 2019. The one on July 8, 2019, was significant because it lasted long enough to receive a number: AR2744. Record-keepers will likely mark it as the first official sunspot of Solar Cycle 25. If so, AR2750 would be the second.

The increasing frequency of new cycle sunspots does not mean Solar Minimum is finished. On the contrary, low solar activity will probably continue for at least another year as Solar Cycle 24 decays and Solar Cycle 25 slowly sputters to life. If forecasters are correct, Solar Cycle 25 sunspots will eventually dominate the solar disk, bringing a new Solar Maximum as early as 2023.

Close Encounter with a Gigantic Jet

Oct. 25, 2019: When you see lightning, run! That’s what NOAA advises in lightning safety brochures. On Oct. 15th, however, pilot Chris Holmes had no place to go when lightning started to crackle in thunderstorms around his aircraft.

“I was flying 35,000 feet over the Gulf of Mexico near the Yucatan Peninsula when a super cell started pulsing with light,” he says. “It wasn’t just ordinary lightning, though. The cell was also creating lots of sprites and jets leaping up from the thunderhead.”

At a distance of only 35 miles, he video-recorded this:


“It was the most amazing thing I’ve seen in my aviation career,” he says.

Holmes had a close encounter with a Gigantic Jet. Sometimes called “Earth’s tallest lightning,” because they reach all the way to the ionosphere ~50 miles high, the towering forms were discovered near Taiwan and Puerto Rico in 2001-2002. Since then, only dozens of Gigantic Jets have been photographed. In previous images taken by cameras on the ground, it’s almost always impossible to see the base of the jet over the edge of the thundercloud. That’s why Holmes’s video is special. He was filming above the storm at practically point-blank range.

“His clip shows very nicely the top of the cloud where the jet emerges, which is usually hidden from view,” says Oscar van der Velde of the Lightning Research Group at the Universitat Politècnica de Catalunya who examined the footage. “I split the video into individual frames so we can see exactly what happens.”


Van der Velde’s deconstruction reveals the order of events: “First, relatively cool blue filaments spring up. These are streamers akin to Saint Elmo’s Fire,” he explains. “Next, after the Jet reaches its maximum height, another feature crawls more slowly out of the cloudtop–a white-hot ‘lightning leader.'”

Turns out, this is a bit of a surprise. For years, some researchers thought that Gigantic Jets could reach such extreme heights only if their streamers got a boost from the lightning leader. Holmes’s video shows just the opposite: The Gigantic Jet reaches the ionosphere before the lightning leader even leaves the cloud.

“This suggests that there may be a much more powerful electric configuration inside the thunderstorm than was previously thought–perhaps as much as 200 million volts,” he says.

It just goes to show, we still have a lot to learn about Gigantic Jets.