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.

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:

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“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.

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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:

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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:

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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:

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“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.”

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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.

 

Cosmic Rays are Nearing a Space Age Maximum

Oct. 3, 2019: Solar Minimum is underway, and it’s a deep one. Sunspot counts suggest it is one of the deepest minima of the past century. The sun’s magnetic field has become weak, allowing extra cosmic rays into the solar system. Neutron monitors at the Sodankyla Geophysical Observatory in Oulu, Finland, show that cosmic rays are percentage points away from a Space Age record:

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Researchers at the Sodankyla Geophysical Observatory have been monitoring cosmic rays since 1964. When cosmic rays hit Earth’s atmosphere, they produce a spray of secondary particles that rain down on Earth’s surface. Among these particles are neutrons. Detectors in Oulu count neutrons as a proxy for cosmic rays.

As the top panel shows, cosmic rays naturally wax and wane with the 11-year solar cycle. During Solar Maximum cosmic rays are weak; during Solar Minimum they are strong. The Space Age record for cosmic rays was set in late 2009-early 2010 near the end of a very deep Solar Minimum.

Records, they say, are meant to be broken. As 2019 comes to a close, neutron counts at Oulu are approaching the very high levels seen in 2009-2010. A new record could be just weeks or months away. This is important because excess cosmic rays pose a health hazard to astronauts and polar air travelers, affect the electro-chemistry of Earth’s upper atmosphere, and may help trigger lightning.

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Because cosmic rays are such an important form of space weather, we’ve added a new data feed to our web site. It’s right here. Every day you can see how Oulu neutron counts are changing. The values are expressed as percentages of the “Space Age average”–that is, the average of all neutron counts since 1964.

This data feed is made possible by the extraordinary dedication and decades-long monitoring program of the Sodankyla Geophysical Observatory in Oulu, Finland. Thank you!

A “STEVE Storm” Hits Scandinavia

Oct. 2, 2019: When a stream of solar wind hit Earth’s magnetic field last Friday, Sept. 27th, forecasters expected an aurora storm around the Arctic Circle. Turns out, it was more of a “STEVE storm.” Many sky watchers in Scandinavia saw the mauve ribbon of light for the very first time. Göran Strand photographed the event from Handöl, Sweden:

“I finally got to see STEVE,” says Strand, who is a veteran observer of auroras, but had never seen STEVE before. “It all started when I noticed a faint green corona outside our mountain cabin. I grabbed my camera gear and headed out into the night. At my first stop along this road I encountered STEVE.”

STEVE (Strong Thermal Emission Velocity Enhancement) looks like an aurora, but it is not. The phenomenon is caused by hot (3000°C) ribbons of gas flowing through Earth’s magnetosphere at speeds exceeding 6 km/s (13,000 mph). These ribbons appear during some geomagnetic storms, revealing themselves by their soft purple/mauve glow.

STEVE normally appears at latitudes around +50N to +55N, on rare occasions dipping down into the +40s. In this case, however, the sightings were at unusually high latitudes, topping +60N in Handöl, Sweden (+63.3N); Ruovesi, Finland (+62.0N); Turku, Finland (+60.5N) and, if we round up a little, Laguja, Estonia (+58.2N). This event shows that the habitat of STEVE may reach farther north than previously thought. Aurora alerts: SMS Text.

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A Summer without Sunspots

Sept. 23, 2019: Could northern summer 2019 go down in history as “the summer without sunspots”? From June 21st until Sept 22nd, the sun was blank more than 89% of the time. During the entire season only 6 tiny sunspots briefly appeared, often fading so quickly that readers would complain to Spaceweather.com, “you’ve labeled a sunspot that doesn’t exist!” (No, it just disappeared.) Not a single significant solar flare was detected during this period of extreme quiet.


The sun on Sept. 22, 2019–as blank as a billiard ball. Credit: NASA/SDO

This is a sign that Solar Minimum is underway and probably near its deepest point. For 2019 overall (January through September), the sun has been blank 72% of the time, comparable to annual averages during the century-class Solar Minimum of 2008 (73%) and 2009 (71%). The current Solar Minimum appears to be century-class as well, meaning you have to go back to the beginning of the 20th century to find lulls in solar activity this deep.

Contrary to the sound of it, “Solar Minimum” is not boring. During this phase of the solar cycle, the sun’s magnetic field weakens, allowing cosmic rays to enter the solar system. This doses astronauts and possibly air travelers with extra radiation. The sun also dims, especially at extreme ultraviolet wavelengths, causing the upper atmosphere to cool and collapse. Space junk accumulates in Earth orbit as a result. Finally, streams of solar wind punch through the sun’s weakening magnetic field, lashing Earth with gaseous material that can cause geomagnetic storms. (One such stream is due later this week on Sept. 27-28.)

Interestingly, the summer of 2019 also brought us a sign that Solar Minimum is coming to an end. One of the numbered sunspots that briefly appeared on July 7th had a reversed magnetic polarity:


Above: A magnetic map of the sun’s surface (AR2744 inset) on July 7, 2019, from NASA’s Solar Dynamics Observatory

According to Hale’s Law, sunspots switch polarities from one solar cycle to the next. This small summertime sunspot was +/- instead of the usual -/+, marking it as a member of the next solar cycle, Solar Cycle 25. Solar Minimum won’t last forever!

Solar cycles always mix together at their boundaries. We can expect to see more new-cycle sunspots in the months ahead as Solar Cycle 24 dies out and Solar Cycle 25 slowly comes to life. If forecasters are correct, the next Solar Maximum will be in full swing by 2023.

The Mysterious Movements of GOES-13

Sept. 11, 2019: Scott Tilley has an unusual hobby. He scans the skies for satellites where they shouldn’t be. Using an S-band receiver, the amateur radio operator has tracked many classified spacecraft orbiting Earth and famously found NASA’s IMAGE satellite when it woke up from the dead last year. This past weekend he bagged another one: GOES-13.

“This was quite a surprise,” says Tilley. “I thought GOES-13 was in a graveyard orbit–yet I found it quite active and wandering on Sept. 8th.”

GOES-13 is a NOAA weather satellite. It was retired in January 2018 after a storied 12-year career during which it monitored some of the most notorious weather events in recent U.S. history – including Hurricane Sandy in 2012 and the triple disaster of Hurricanes Harvey, Irma and Maria in 2018. The satellite also experienced significant space weather: In December 2006, GOES-13 observed a solar flare so intense it damaged its onboard Solar X-ray Imager.

When weather satellites are retired, they are typically steered into a high parking orbit for storage. GOES-13 was reportedly “parked” over longitude 60W. But that’s not where Tilley found it.


Above: GOES-13 S-band signals received by Scott Tilley on Sept. 8, 2019.

“It was drifting westward through longitude 135W,” he says. “As it was emitting strong radio signals it seemed to me it was going somewhere and with no public statements I could find about this it encouraged me to start an observing campaign.”

Tilley quickly focused his attention on the night of Sept. 9th when the satellite would drift through Earth’s shadow–essentially experiencing a solar eclipse. Would the solar powered satellite survive the blackout?

“Indeed it did,” reports Tilley. “Strong radio transmissions continued before, during and after the eclipse. GOES-13 still has a working battery.”


Above: GOES-13’s response to a solar eclipse, indicating what appears to be nominal battery operation.

This is significant, Tilley explains, because “satellite batteries are sometimes intentionally disconnected as part of their retirement process.  The idea is to ensure the battery doesn’t explode or do something else unwelcome after the system is shutdown and create unintentional space debris. In my mind, a good battery seals the notion that GOES-13 is operational.”

But what is the operation? Tilley suspects that GOES-13 may have been drafted by the US military. News reports earlier this year suggested that the US Air Force is interested in using retired weather satellites as observing platforms. Before GOES-13 was “retired,” its visual imaging system was still fully functioning.

“Only time will tell where GOES-13 ends up,” says Tilley. “But given the nature of these observations there is no doubt in my mind the spacecraft is alive and under intelligent control. The question is, who is the intelligence?”

For a fuller discussion of Tilley’s observations, check out his blog post.

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