Earth Can Makes Its Own Auroras

Sept. 20, 2021: No solar storms? No problem. Earth has learned to make its own auroras. New results from NASA’s THEMIS-ARTEMIS spacecraft show that a type of Northern Lights called “diffuse auroras” comes from our own planet–no solar storms required.

Diffuse auroras look a bit like pea soup. They spread across the sky in a dim green haze, sometimes rippling as if stirred by a spoon. They’re not as flamboyant as auroras caused by solar storms. Nevertheless, they are important because they represent a whopping 75% of the energy input into Earth’s upper atmosphere at night. Researchers have been struggling to understand them for decades.

Above: Diffuse auroras and the Big Dipper, photographed by Emmanuel V. Masongsong in Fairbanks, AK

“We believe we have found the energy source for these auroras,” says UCLA space physicist Xu Zhang, lead author of papers reporting the results in the Journal of Geophysical Research: Space Physics and Physics of Plasmas. “It is Earth itself.”

Earth performs this trick using electron beams. High above our planet’s poles, they shoot upward into space, accelerated by electric fields in Earth’s magnetosphere. Sounding rockets and satellites discovered the beams decades ago. It turns out, they can power the diffuse auroras.

The video, below, shows how it works. Electron beams travel in great arcs through the space near Earth. As they go, they excite ripples in the magnetosphere called Electron Cyclotron Harmonic (ECH) waves. Turn up the volume and listen to the waves recorded by THEMIS-ARTEMIS:

Above: A great electrical circuit in space powering diffuse auroras. ECH waves were sonified by NASA’s HARP (Heliophysics Audified: Resonances in Plasmas) software.

ECH waves, in turn, knock other electrons out of their orbits, forcing them to fall back down onto the atmosphere. This rain of secondary electrons powers the diffuse auroras.

“This is exciting,” says UCLA professor Vassilis Angelopoulos, a co-author of the papers and lead of the THEMIS-ARTEMIS mission. “We have found a totally new way that particle energy can be transferred from the Earth’s own atmosphere out to the magnetosphere and back again, creating a giant feedback loop in space.”

According to Angelopoulos, Earth’s polar electron beams sometimes weaken but they never completely go away, not even during periods of low solar activity. This means Earth can make auroras without the sun.

The sun is currently experiencing periods of quiet as young Solar Cycle 25 sputters to life. Pea soup, anyone?

The original research may be read here and here.

Inspiration 4: Historic Space Mission Blasts Off

Sept. 16, 2021: SpaceX just made history again. On Sept. 15th, a Falcon 9 rocket blasted off from Cape Canaveral carrying the first all-civilian crew to Earth orbit. “It was spectacular,” reports Bill Williams of Titusville, Florida. “Shooting from the west side of the Indian River, I recorded exhaust plumes and a dramatic ‘rocket nebula’ in the moonlit dusk skies.”

“I would rather have been on the rocket,” says Williams, “but the view from Earth wasn’t bad either!”

This mission, named “Inspiration4,” is setting a number of milestones. First of all, there are no astronauts onboard. It’s the first orbital spaceflight crewed entirely by private citizens. One of them, Hayley Arceneaux, age 29, is the youngest American ever to go to space. All 4 citizens received astronaut training from SpaceX, including orbital mechanics, microgravity exercises and mission simulations.

Arceneaux is also a pediatric cancer survivor, and the flight is raising money for childhood cancer research. The seat next to her on the spacecraft was raffled off, raising $200 million for the St. Jude Children’s Research Hospital, where Arceneaux’s life was saved years ago.

Above: The crew capsule with its bubble-shaped window

To top it all off, the crew are orbiting higher than any astronauts since STS-125 in 2009. They’re actually above the International Space Station.

If all goes as planned, the capsule will be in Earth orbit until Sept. 19th. One end of the spacecraft has a bubble-shaped window, giving the space travelers an unparalleled view of Earth. Here on the ground, we can look up and see them, too. The capsule is about as bright as a 3rd magnitude star, easy to spot from rural areas. For local flyby predictions, check Heavens Above.

Solar Tsunami and CME

Aug. 27, 2021: Sunspot AR2859 erupted on Aug. 26th, producing a C3-class solar flare: movie. The flare, however, was not the main attraction. The eruption also caused a massive “solar tsunami.” Watch the shadowy wave ripple across the sun in this false-color ultraviolet movie from NASA’s Solar Dynamics Observatory:

The expanding circular shadow is a wave of hot plasma and magnetism. Based on the time it took to reach the next sunspot, halfway around the sun, the tsunami was traveling faster than 110,000 mph.

Solar tsumanis always herald a CME, and this one was no exception. Soon after the tsunami broke, SOHO coronagraphs detected a plasma cloud leaving the sun: movie.

Update: NOAA analysts have modeled the CME’s trajectory. They predict an Earth impact during the late hours of Aug. 29th, possibly sparking G1-class geomagnetic storms through midday on Aug. 30th.   Aurora alerts: SMS Text.

SOLAR RADIO BURST: When sunspot AR2659 exploded on Aug. 26th, shortwave loudspeakers on the dayside of Earth erupted with static. “It was a solar radio burst,” reports Thomas Ashcraft, who recorded the sounds from his observatory in rural New Mexico. Click to listen:

Take another look at the “solar tsunami,” above. Much of the static Ashcraft recorded is caused by that shock wave rippling through the sun’s atmosphere. Plasma waves in the ionized corona naturally emit radio noise. Ham radio operators, military radar installations, and radio astronomers have been picking up these sounds since the 1940s. You can do it yourself from your own backyard.

“As I write, the sun just produced another very strong radio burst, which really packed a punch on my spectrograph!” says Ashcraft. In other words, stay tuned for more…

Perseid Meteor Outburst

Aug. 18, 2021: 28 years ago, the Perseid meteor shower killed a satellite. On Aug. 11, 1993, a Perseid meteoroid hit the Olympus-1 telecommunications satellite, making it spin. The $850 million spacecraft was lost after it ran out of fuel trying to regain control.  Many researchers blame a dense ribbon of comet dust now known as “the Perseid Filament.”

This week, the Perseid Filament came back. Probably.

Above: The Perseid outburst of Aug. 14, 2021, captured by Carl Bracken of the Cedar Amateur Astronomers in Iowa using his AMS42 camera. More images.

On Aug. 14, 2021, night skies over North America filled with meteors. P.  Martin of Ottawa, Canada, reported “multiple Perseids per minute with many bursts, sometimes 3-4 in a second.” In San Diego, Robert Lunsford of the International Meteor Organization also witnessed rapidfire streaks, 2 to 3 at a time. “It made me realize something unusual was going on,” Lunsford says, “especially so far from the predicted maximum.”

To say that astronomers were surprised would be an understatement. The Perseid’s annual peak had occurred the night before. Most observers had already given up watching. Fortunately, a network of automated cameras operated by the Cedar Amateur Astronomers in Iowa captured the display. Overnight they recorded almost 3000 meteors.

Above: Meteor rates during the 2021 outburst. More.

Peter Jenniskens, an astronomer at the SETI Institute and NASA/Ames, believes it may have been the Perseid Filament. “I think so,” he says. “The width of the outburst is similar to that of past Perseid Filament returns.”

The Perseid Filament is a ribbon of dust inside the broader Perseid debris zone. Comet 109P/Swift-Tuttle supplies the raw material. The comet loops around the sun every 133 years, shedding dust as it goes. Over time, much of Swift-Tuttle’s dust is perturbed by the gravity of Jupiter, helping scatter it into the diffuse cloud that we experience every year as the Perseid meteor shower. But there is a part of the comet’s orbit in a “mean motion resonance” with Jupiter where dust can accumulate instead of dispersing. This is the Perseid Filament.

Forecasters still can’t predict when the Perseid Filament will return. It came for many years in a row around 1993, and it may have grazed Earth again, slightly, in 2018, 2019 and 2020. No one predicted a direct hit in 2021.

This uncertainty naturally raises the question: Was it really the Filament? The jury’s still out. Observers may have stumbled upon an entirely new ribbon of Perseid dust. Either way, researchers are looking forward to next year to see if it comes back again. And they probably won’t stop watching when the peak is “done.”

Blue Lightning in the Stratosphere

Aug. 15, 2021: Rain. Clouds. Thunder. The stratosphere has none of those things. Weather up there is pretty dull. Except when the lightning starts….

Researchers call them “blue jets.” The elusive discharges leap into the stratosphere from thunderstorms far below. They are rarely seen, but storm chaser Rob Neep was able to capture some over Sonora, Mexico, on August 3rd:

“I couldn’t believe my eyes,” says Neep, a former TV photojournalist. “I was actually looking for sprites when the jets appeared. They were definitely visible to the naked eye, both my cousin and I observed them.”

Oscar van der Velde of the Lightning Research Group at the Universitat Politècnica de Catalunya watched Neep’s video and says it is “Excellent–perhaps the best example of classic blue jets we’ve seen in a long time!”

First recorded by cameras on the space shuttle in 1989, blue jets are part of a growing menagerie of transient luminous events (TLEs) in the upper atmosphere. They appear alongside sprites, ELVES, and other lightning-like forms. Blue jets, however, seem to be more elusive than the others, often frustrating photographers who try to catch them.

“We’re not sure why ground-based observers see them so rarely,” says van der Velde. “It might have something to do with their blue color. Earth’s atmosphere naturally scatters blue light, which makes them harder to see. Neep’s video was taken from a relatively high altitude site (elevation 3500 ft); thin clear air probably helped.”

“Not all storms have blue jets,” he allows. “Even so, blue jets may be much more common than we think.”

Above: Artist’s concept of a blue jet observed from the ISS. Credit: DTU Space, Daniel Schmelling/Mount Visual

In 2018, SpaceX launched Europe’s Atmosphere-Space Interactions Monitor (ASIM) to the International Space Station to study TLEs from space. Data from ASIM show that blue jets can leap as high as 170,000 feet above the ground. They’re sparked by mysterious “blue bangs“–brilliant blue flashes in the tops of thunderclouds possibly caused by intense turbulence.

It’s important to study blue jets because, according to van der Velde, “there can be considerable production of NOx and ozone by these discharges, potentially affecting the chemistry of the atmosphere.” Also, some blue jets might rise high enough to touch the ionosphere, forming a new and poorly understood branch of the global electrical circuit.

And on top of everything else, “they’re beautiful,” says Neep. “I was lucky to catch some.”

Rare Naked-Eye Nova

August 9, 2021: Every 20 years or so, a thermonuclear explosion occurs on the surface of RS Oph, a white dwarf in the constellation Ophiuchus. Yesterday, it happened again. On Aug. 8th, the brightness of the tiny star increased 600-fold, from magnitude +12 to +5. Keith Geary of Ireland was the first to notice. Hours later, Italian astronomer Ernesto Guido and colleagues photographed the outburst using a remote-controlled telescope in Australia:

This is called a “recurrent nova,” and it is rare. In the whole Milky Way galaxy, only 7 star systems are known to produce such explosions.

RS Oph is actually a binary star–a very lopsided one. On one side is a white dwarf, on the other is a red giant. There’s very little distance between the two, so the gravity of the white dwarf is able to pull gaseous material off the larger star down onto itself. Every couple of decades, enough matter accumulates to trigger an explosion. The last time this happened was back in 2006.

At 5th magnitude, the current outburst is visible to the unaided eye, albeit just barely. Binoculars or a telescope will allow you to see it with ease. Look south after sunset. Ophiuchus hangs high in the sky just above the better known constellations Scorpius and Sagittarius. Sky maps: simple, detailed, really detailed.

Update: Variable star observer Filipp Romanov of Yuzhno-Morskoy, Russia, has just seen RS Oph and estimates that its magnitude has increased further to +4.6.

Solar Max Might Come a Year Early

Aug. 3, 2021: Solar Cycle 25 is heating up faster than expected. The latest sign may be found in sunspot counts from July 2021. Continuing a trend that started last year, they overperform the official forecas

Issued by the NOAA/NASA Solar Cycle 25 Prediction Panel in 2019, the official forecast calls for Solar Cycle 25 to peak in July 2025. However, a better fit to current data shows Solar Cycle 25 peaking in October 2024. This is just outside the 8-month error bars of the Panel’s forecast.

July 2021 was a remarkable month. Solar Cycle 25 crossed multiple thresholds, including its first X-flare and, at one point, 6 sunspots on the solar disk. The last time so many sunspots were seen at the same time was Sept. 2017 (SWx archive). One farside CME in July was so strong it affected Earth despite being on the “wrong” side of the sun. A handful of other CMEs narrowly missed our planet.

If solar activity increases apace, some of those blows will soon begin to land. Stay tuned.

Nuclear Bombs Can Cause Geomagnetic Storms

July 29, 2021: They called it “Starfish Prime.” On July 9, 1962, the US military exploded a thermonuclear warhead 250 miles above the Pacific Ocean. What happened next surprised everyone.

Witnesses from Hawaii to New Zealand reported auroras dancing overhead, magnificent midnight “rainbow stripes” that tropical sky watchers had never seen before. Radios fell silent, then suddenly became noisy. Burglar alarms sounded as local streetlights in Honolulu went black.

Above: ‘Nuclear auroras’ viewed from Honolulu (left) and from a surveillance aircraft (right) on July 9, 1962.

Starfish Prime essentially created an artificial solar storm complete with auroras, geomagnetic activity, and blackouts. Much of the chaos that night was caused by the electromagnetic pulse (EMP)–a ferocious burst of radiation that can ionize the atmosphere and pepper the ground below with secondary particles akin to cosmic rays. Government and industry researchers have been studying the Starfish Prime EMP for decades.

A new paper just published in the research journal Earth and Space Science suggests they might be overlooking something.

“Typical EMP simulations found in government and industry reports use over-simplified models of the Earth,” says lead author Jeffrey Love of the United States Geological Survey. “They do not provide accurate estimates of the hazard in complex geological settings.”

In their paper, Love et al describe how a high-altitude nuclear blast jerks Earth’s magnetic field. First, the EMP ionizes a layer of air underneath the bomb. This layer presses downward, pinning Earth’s magnetic field lines in their pre-blast locations. Next, as the ionization subsides, the magnetic field springs back. It’s a sort of heaving, lurching geomagnetic storm.

Geomagnetic storms are famous for causing power blackouts. Usually the sun is to blame, but EMPs can do it, too. Lurching magnetic fields cause electrical currents to flow through the ground. Literally, rocks beneath your feet begin to tingle with electricity. These currents, in turn, make their way into grounded electric-power grids, potentially damaging transformers and blacking out power supplies.

Above: A geological map of the midcontinental USA. Triangle mark places where magnetotelluric measurements have been made.

The crucial point of Love’s paper is this: Earth is not the same everywhere. In recent years, researchers have been sounding Earth’s crust to determine the 3D electrical properties of our planet. These magnetotelluric surveys reveal huge variations in conductivity from place to place, depending on the mix of underlying rock. 

Love has been one of the pioneers in applying this type of Earth data to space weather, predicting how global geomagnetic storms might affect local power lines. Now he and his colleagues are doing the same with EMPs.

The team focused their attention on the eastern midcontinental USA, a region bracketed by St. Louis, Missouri, and Memphis, Tennessee. Between 2016 and 2019, the USGS conducted a magnetotelluric survey of the area, so the data are fresh. The terrain is remarkable for its mix of rock types. Underneath it all is a layer of Precambrian basement rock, which is electrically resistive; this is overlain by differing depths of younger, electrically conductive sedimentary rock. Notable features include the Ozark Dome, where the sedimentary layer is thin, and the Reelfoot Rift, which is deeply filled with sedimentary rock.

Love’s team simulated a nuclear explosion about 300 km above this region. They found a huge range of geoelectric responses. Some power lines in the simulation had excess voltages near 2000 V, while others were closer to 0 V. Both were sharp departures from previous studies.

“Given the results of our analysis for the Eastern Midcontinent, it is reasonable to envision performing similar analyses for other places,” the authors conclude. A geophysicists’s work is never done…

Read the original research at https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2021EA001792

The Alpha Capricornid Meteor Shower

July 24, 2021: Today, meteor storms are rare, but a few hundred years from now they could be commonplace. Consider this fireball, recorded by Thomas Ashcraft on July 21st, a preview of things to come:

“This is a probable alpha Capricornid,” says Ashcraft, who operates an automated meteor camera in rural New Mexico. “It was magnitude -11, about as bright as a waxing gibbous Moon.” Next: Turn up the volume. The soundtrack is a 54.309 MHz digital TV signal reflected from the fireball’s ionized trail.

Alpha Capricornid meteors are debris from Comet 169P/NEAT. They appear every year in late July, peaking around the July-August boundary with 5 to 9 meteors per hour. Many “alpha Caps” are slow, bright fireballs.

This is a minor shower today, but in the not-too-distant future, it could turn into a regular meteor storm. Researchers Peter Jenniskens (SETI Institute) and Jeremie Vaubaillon (Paris Observatory) have studied the alpha Capricornid debris stream. They believe it resulted from a major fragmentation event ~5000 years ago when as much as half of the original comet disintegrated. Since then, the debris has been drifting toward Earth.

“In the next 300 years, the alpha Capricornids are likely to grow into a major annual shower,” they write in an article in the Astronomical Journal. “Rates will increase dramatically in the 23rd and 24th centuries to a peak of ZHR = 2200/hr on an annual basis, half the visible shower peak rate during the 1999 Leonid storm.”

If they’re right, every alpha Capricornid we see today heralds a storm to come. Watch for them in the nights ahead slowly spilling out of the constellation Capricornus. The best time to look is during the hours around midnight when the shower’s radiant may be found in the southern sky beautifully bracketed by Jupiter and Saturn: sky map.

Bonus: Another meteor shower, the southern Delta Aquarids (SDAs), also peaks in late July, sending streaks of light from the same general part of the sky. SDAs zip along ~twice as fast as alpha Caps and tend to be fainter. Nevertheless, they will add to your midnight meteor count. Enjoy!

NLCs Setting Records

July 21, 2021: Noctilucent cloud (NLC) season is now 8 weeks old. This animation from NASA’s AIM spacecraft shows everything that has happened since the first clouds appeared in late May:

The last frame says it all: Noctilucent clouds are still bright and abundant. In fact, at the highest latitudes they are setting records.

“We’re seeing more clouds at 80°N than in any other year since AIM was launched,” says Cora Randall of the University of Colorado’s Laboratory for Atmospheric and Space Research. “Cloud frequencies at 80°N are around 85%, whereas it’s more typical to see frequencies of about 75%.” (‘Frequencies’ are a measure of patchiness. 100% is complete coverage; 0% is no clouds at all.)

“This morning, I watched a fantastic display, the best of the year so far ,” reports Marek Nikodem, who photographed the clouds from Szubin, Poland (53°N) on July 21st:

“It’s not the end of the season yet,” he says. Indeed, it’s not.

NLCs are Earth’s highest clouds. They form when summertime wisps of water vapor rise up to the edge of space, about 83 km high, and crystalize around disintegrated meteoroids. When you see one, you’re literally seeing a cloud of frosted meteor smoke.

Earlier this summer, NLCs were seen in Europe as far south as the mediterranean coast of Spain (+37N). Given the current surge, another low-latitude excursion cannot be ruled out before the season ends in August. Watch for them!