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.

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.

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!

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.

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.