Magnetic Explosions Discovered on Earth’s Doorstep

Jan. 16, 2019: Yes, there are explosions in Earth’s magnetic field. They happen all the time. Gusts of solar wind press against Earth’s magnetosphere, squeezing lines of magnetic force together. The lines criss-cross and reconnect, literally exploding and propelling high energy particles toward Earth.  Auroras are the afterglow of this process.

On Dec. 20, 2015, one such explosion occurred closer to Earth than anyone had seen before.  It has taken researchers 4 years to fully wrap their minds around what happened, and the results were published just this week in the Jan. 13, 2020, edition of Nature Physics.

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Auroras in the aftermath of a near-Earth magnetic explosion on Dec. 20, 2015. Credit: Joseph Bradley of Whitehorse, Yukon, Canada

Lead author Vassilis Angelopoulos of UCLA explains: “Usually, these explosions happen at least 100,000 miles from Earth, far downstream in our planet’s magnetic tail. On Dec. 20, 2015, however, we observed a reconnection event only 30,000 miles away–more than 3 times closer than normal.”

It was a case of good luck and perfect timing. NASA’s swarm of three THEMIS spacecraft were passing through the area, and they were able to pinpoint the explosion’s location “right on the doorstep” of the geosynchronous satellite belt. This showed reconnection events may pose a previously overlooked threat to Earth-orbiting satellites. The nearby blast caused a strong G2-class geomagnetic storm and intense auroras around the Arctic Circle.

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In this diagram of Earth’s magnetosphere, “X” marks the spot of the Dec. 20, 2015, explosion. The 3 THEMIS spacecraft are also shown. Credit: Emmanuel Masongsong, UCLA EPSS

Angelopoulos estimated the energy involved. “The explosion and subsequent storm delivered as much as ~88 PetaJoules of energy to the near-Earth environment. That’s more than 10 times the energy of the largest US nuclear bomb and about 20 times the energy of a magnitude 7 earthquake.”

Before this event, many researchers felt that reconnection at such proximity was impossible. Earth’s nearby magnetic field was too stable for such explosions … or so the thinking went.

“Now we know better,” Angelopoulos says. “The THEMIS multipoint observations are iron-clad. It really happened, and this is going to make a big impact on future studies of geomagnetic storms.”

The original research in Nature Physics may be found here.

 

The Fainting of Betelgeuse — Update

Jan. 10, 2020: One day, perhaps in our lifetimes, perhaps a million years from now, the red giant Betelgeuse will dim a little–and then explode. The resulting supernova will rival the full Moon and cast shadows after dark, completely transforming the night skies of Earth. No wonder astronomers are closely tracking the current “fainting of Betelgeuse.”

“Fainting” is an actual astronomical term. It means dimming, the opposite of brightening. And right now, Betelgeuse is definitely fainting.

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 Betelgeuse photographed by Brian Ottum of Animas, New Mexico, almost 4 years apart using the same telescope and observing methods. 

Edward Guinan of Villanova University and colleagues caused a minor sensation last month when they reported “[Betelgeuse] has been declining in brightness since October 2019, now reaching a modern all-time low of V = +1.12 mag on 07 December 2019 UT. Currently this is the faintest the star has been during our 25+ years of continuous monitoring.”

Little did they know when they issued their telegram in December that Betelgeuse was about to become even fainter. “On 06 January 2020 UT, the magnitude of Betelgeuse was V = +1.37,” reports Guinan. That’s 20% dimmer than the “modern all-time low” registered last month.

This 3-year plot of the Villanova team’s data shows Betelgeuse’s rapid decline:

magnitudes

The horizontal axis is Heliospheric Julian Date (HJD). For reference, Jan. 6, 2020, the date of the most recent measurement, has an HJD of 2458855.

The fainting is easy to see with the naked eye. Not too long ago, Betelgeuse was the 10th brightest star in the sky. Now it is the 21st. Observers of Orion rising in the east after sunset can’t help but notice that the Hunter’s shoulder is dimmer than it used to be.

Astronomers have long known that Betelgeuse is on the precipice of an energy crisis. It’s about to run out of fuel in its core. When that happens, the star will collapse and rebound explosively, producing the first bright supernova in the Milky Way since 1604. Experts in stellar evolution believe Betelgeuse could die at any time during the next 100,000 years or so–a blink of an eye on time scales of astronomy.

Does the current dimming herald that final blast? Probably not. Betelgeuse is a slowly variable star, and this is probably no more than an episode of deeper-than-usual dimming. Of course, one day astronomers will think the same thing … and then the night sky will change forever.

Stay tuned for updates.

Polar Stratospheric Clouds Continue

Jan. 9, 2020: The finest outbreak of polar stratospheric clouds (PSCs) in decades is still going strong. “We witnessed a wonderful display this evening (Jan. 8th),” reports Alex Conu, who photographed the clouds drawing a crowd in Oslo, Norway:

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“The cloud’s bright pastel colors looked fabulous alongside Venus in the evening sky,” he says.

Polar stratospheric clouds are rare. Normally, the stratosphere has no clouds at all. A few times each winter, however, icy clouds form when the temperature in the stratosphere drops below -85C. Such staggeringly-low temperatures are required to help sparse water molecules stick together. This winter, the clouds have been appearing daily since late December, a sign of unusually cold conditions in the stratosphere.

Stratospheric clouds are widely regarded as the most beautiful clouds on Earth. Because of their intense colors (caused by high-altitude sunlight hitting tiny ice crystals), novice sky watchers sometimes mistake the clouds for auroras. This picture from P-M Hedén of Tänndalen, Sweden, shows why:

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“On Jan. 4th, the colors got so strong that the snow turned red,” marvels Hedén. “I have been seeing these crazy displays at both sunrise and sunset from my cabin in the Swedish mountains.”

Stay tuned for updates as the outbreak continues.

Electricity Surges Through the Soil of Norway

Jan. 7, 2019: Yesterday, Jan. 6th, something unexpected happened in the soil of northern Norway. “Electrical currents started flowing,” reports Rob Stammes, who monitors ground currents at the Polarlightcenter geophysical observatory in Lofoten. This chart recording shows the sudden surge around 1930 UT:

“It seemed to be some kind of shockwave,” says Stammes. “My instruments detected a sudden, strong variation in both ground currents and our local magnetic field. It really was a surprise.”

NASA’s ACE spacecraft detected something as well. About 15 minutes before the disturbance in Norway, the interplanetary magnetic field (IMF) near Earth abruptly swung around 180 degrees, and the solar wind density jumped more than 5-fold. Earth may have crossed through a fold in the heliospheric current sheet–a giant, wavy membrane of electrical current rippling through the solar system. Such crossings can cause these kind of effects.

While currents flowed through the ground, auroras filled the sky. Rayann Elzein photographed the corresponding outburst of lights from Utsjoki, Finland:

“What a surprise!” says Elzein. “The auroras were sudden and dynamic, with fast-moving green needles and several purple fringes!”

The auroras and ground currents were caused by the same thing: Rapidly changing magnetic fields. High above Earth’s surface, magnetic vibrations shook loose energetic particles, which rained down on the upper atmosphere, creating auroras where they struck. Just below Earth’s surface, magnetic vibrations caused currents to flow, triggering Rob Stammes’ ground sensors.

“We couldn’t see the auroras in northern Norway because of cloud cover,” says Stammes, a little ruefully. “We had to be satisfied with the electricity underfoot.”

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A New Year’s Outbreak of Polar Stratospheric Clouds

Jan. 1, 2020: A spectacular display of polar stratospheric clouds (PSCs) that began two days ago is still going strong around the Arctic Circle. This picture, taken on Dec. 31st by Per-Anders Gustavsson in Jukkasjärvi, Sweden, shows why some onlookers mistake them for daytime auroras:

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“The colors were amazing,” says Gustavsson, who drives a tour bus for Visit Abisko. “I was driving by the world-famous Ice Hotel when we saw the clouds. We just had to stop for pictures.”

“I’ve seen a lot of beautiful things during my years in the Arctic,” he adds. “This was easily one of the greatest displays I have ever seen.”

Polar stratospheric clouds are newsworthy because normally the stratosphere has no clouds at all. 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.

The clouds are even visible at night, as shown in this Dec. 31st photo taken by Fredrik Broms in Kvaløya, Norway:

Fredrik-Broms-PSC_Kvaloya_Norway_31dec2019_FredrikBroms-2_1577795662

“Better than New Year fireworks – by far!” says Broms. “What an amazing way to end 2019.”

“This really is a rare event,” says Chad Blakley, who runs the Lights over Lapland aurora tour service in Abisko, Sweden. “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. At one point I would say that close to 25% of the sky was filled with the clouds. PSCs we have seen in previous winters have been closer to 1% or 2%.”

Polar stratospheric clouds 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.

“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:

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“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:

e2s2

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.

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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:

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“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.”

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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.”

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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.