Rare Videos of STEVE

April 11, 2018: Yesterday, a G1-class geomagnetic storm was brewing over Canada as a stream of solar wind buffeted Earth’s magnetic field. Matthew Wheeler of Robson Valley, British Columbia, stepped outside to see what was up–and STEVE appeared. “My dog barked at it for the entire hour it was visible,” says Wheeler. “It was flowing like a river at astonishing speed.” Click to play his must-see video:

STEVE may look like an aurora, but it is not. For one thing, it is soft purple, not green like typical auroras. And it has its own special form–tightly collimated into a narrow ribbon that can bisect the entire sky.

Researchers are only beginning to understand the phenomenon–aided by a chance encounter between STEVE and a European satellite a few years ago. In situ measurements revealed that STEVE is a hot (3000 degrees C) ribbon of ionized gas slicing through Earth’s upper atmosphere some 300 km above the ground. It appears unpredictably during some, but not all, geomagnetic storms.

Another video–“my best yet,” says Wheeler–shows the beautiful interaction between the soft-purple ribbon and nearby green “picket fence” auroras:

“The purple ribbon was moving much faster than the green pickets,” says Wheeler. “And while their forms varied from smooth to ragged and back again, their path across the sky was almost constant for the whole hour–as it has since I first noticed STEVE over this valley in the 1980s.”

Does STEVE really make dogs bark? “Mine does,” says Wheeler. “In addition to barking at STEVE, my giant Akbash astronomy dog, Patch, has barked at the space station since he was a pup, and proudly seen it off the farm every time. He is also a valuable spotter of meteor showers. When I hear him barking upwards, it is time to go outside.”

Realtime Aurora Photo Gallery

China’s Doomed Space Station

March 26, 2018: China’s Tiangong-1 space station is about to return to Earth–as a massive fireball. According to the European Space Agency (ESA), the 8-ton spacecraft will re-enter the atmosphere sometime between March 30th and April 2nd. Tiangong-1 is about the size of a European cargo spacecraft, such as the ATV-1 which itself re-entered in 2008. This re-entry video of the ATV-1 shows what the Tiangong-1 fireball might look like:

Tiangong-1 was launched in Sept. 2011 to establish a foothold in Earth orbit for China’s fledgling space program. It served as a temporary home in space for two crews, including China’s first female astronauts, and provided a testbed for automated rendezvous and docking procedures. China lost control of Tiangong-1 in 2016 when a telemetry link failed. This made it impossible for mission controllers to guide the station to a re-entry over the South Pacific Ocean as originally planned. Instead, Tiangong-1 would re-enter on its own schedule as aerodynamic friction with Earth’s upper atmosphere slowly drained the station’s orbital energy.

Initially, Chinese officials speculated that re-entry would occur in late 2017. However, low solar activity delayed the splashdown. Sunspot numbers have plummeted recently as the solar cycle heads toward a deep solar minimum:

Without sunspots, the sun’s extreme ultraviolet radiation decreased. Earth’s upper atmosphere cooled and contracted, reducing aerodynamic friction that would otherwise bring Tiangong-1 down. “Late 2017” became the spring of 2018.

At the moment it is impossible to predict exactly where Tiangong-1 will re-enter. All we know is that it will disintegrate somewhere between +42.8 and -42.8 degrees latitude, the upper and lower limits of the station’s tilted orbit. This map from the ESA shows the re-entry zone:

Even with an uncontrolled re-entry, the odds strongly favor a descent over uninhabited land or ocean. According to the ESA, “[surviving fragments] will be scattered over a curved ellipsoid that is thousands of km in length and tens of km wide. The personal probability of being hit by a piece of debris from the Tiangong-1 is actually 10 million times smaller than the yearly chance of being hit by lightning.”

In other words, don’t worry. You’ll be lucky just to see the fireball. Approximately one day before the reentry, it will become possible to roughly predict re-entry ground tracks, and hence which regions on Earth might witness the disintegration. Stay tuned for updates.

Strange Aurora-like Arc Sighted over Alaska: It’s “Steve”!

March 25, 2018: Last night, something happened at the edge of space over Alaska. More than 200 km above Anchorage, a hot ribbon of ionized gas sliced through Earth’s magnetosphere, creating a luminous arc that rivaled the Moon in brightness. Sanjana Greenhill witnessed the apparition:

“We noticed this perfect arc developing across the sky,” says Greenhill. “It didn’t seem like the aurora since it wasn’t moving much. The arc got brighter and then faded and then got brighter again. And then it dawned on me, this is STEVE!”

STEVE is an aurora-like phenomenon that researchers are only beginning to understand. For many years, northern sky watchers reported the form occasionally dancing alongside auroras. It was widely called a “proton arc” until researchers pointed out that protons had nothing to do with it. So members of the Alberta Aurora Chasers group gave it a new name: “Steve” (since upgraded to STEVE, an acronym for ‘Strong Thermal Emission Velocity Enhancement’).

The first clues to the nature of STEVE came in 2016 when one of the European Space Agency’s Swarm satellites encountered the phenomenon. “As the satellite flew straight though ‘Steve,’ the temperature jumped by 3000°C and the data revealed a 25 km-wide ribbon of gas flowing westwards at about 6 km/s (13,000 mph),” reports Eric Donovan from the University of Calgary.

Donovan and a team of colleagues led by Elizabeth MacDonald of NASA’s Goddard Space Flight Center have just published a paper on STEVE. In it, they confirm that STEVE is distinct from ordinary auroras, usually forming to the south of active Northern Lights. The mauve and purple colored arcs, they say, are related to supersonic rivers of gas called “subauroral ion drifts” (SAIDs), which flow through Earth’s magnetic field. Earth-orbiting satelites have tracked thousands of SAIDs: they tend to appear near latitude +60 degrees, and occur more frequently during spring and fall than summer and winter.

This last point means that now is the season for STEVE. The onset of northern spring seems to lure the arc out of winter hiding.

“I saw STEVE for the first time on March 18th,” reports Giuseppe Petricca , who took this sequence of pictures from the Isle of Lewis in Scotland:

“It was an ever-changing tornado, with violet tones, always in movement, always with different shapes,” he says. “Another wonder of Nature!”

The mystery of STEVE is far from solved. Researchers still don’t understand why STEVE is purple–or for that matter why the underlying rivers of gas should glow at all. “Further spectral analysis and modeling are needed,” say MacDonald et al.

In other words, keep an eye out for STEVE.

Realtime “Steve” Photo Gallery

 

“Equinox Cracks” Forming in Earth’s Magnetic Field

March 11. 2018: The vernal equinox is less than 10 days away. That means one thing: Cracks are opening in Earth’s magnetic field. Researchers have long known that during weeks around equinoxes fissures form in Earth’s magnetosphere. Solar wind can pour through the gaps to fuel bright displays of Arctic lights. One such episode occurred on March 9th. “The sky exploded with auroras,” reports Kristin Berg, who sends this picture from Tromsø, Norway:

During the display, a stream of solar wind was barely grazing Earth’s magnetic field. At this time of year, that’s all it takes. Even a gentle gust of solar wind can breach our planet’s magnetic defenses.

This is called the the “Russell-McPherron effect,” named after the researchers who first explained it. The cracks are opened by the solar wind itself.  South-pointing magnetic fields inside the solar wind oppose Earth’s north-pointing magnetic field. The two, N vs. S, partially cancel one another, weakening our planet’s magnetic defenses. This cancellation can happen at any time of year, but it happens with greatest effect around the equinoxes. Indeed, a 75-year study shows that March is the most geomagnetically active month of the year, followed closely by September-October–a direct result of “equinox cracks.”

NASA and European spacecraft have been detecting these cracks for years. Small ones are about the size of California, and many are wider than the entire planet. While the cracks are open, magnetic fields on Earth are connected to those on the sun. Theoretically, it would be possible to pick a magnetic field line on terra firma and follow it all the way back to the solar surface. There’s no danger to people on Earth, however, because our atmosphere protects us, intercepting the rain of particles. The afterglow of this shielding action is called the “aurora borealis.”

Stay tuned for more Arctic lights as spring approaches.

Realtime Aurora Photo Gallery

The Worsening Cosmic Ray Situation

March 5, 2018: Cosmic rays are bad–and they’re getting worse.

That’s the conclusion of a new paper just published in the research journal Space Weather. The authors, led by Prof. Nathan Schwadron of the University of New Hampshire, show that radiation from deep space is dangerous and intensifying faster than previously expected.

cr_strip

The story begins four years ago when Schwadron and colleagues first sounded the alarm about cosmic rays. Analyzing data from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument onboard NASA’s Lunar Reconnaissance Orbiter (LRO), they found that cosmic rays in the Earth-Moon system were peaking at levels never before seen in the Space Age. The worsening radiation environment, they pointed out, was a potential peril to astronauts, curtailing how long they could safely travel through space.

This figure from their original 2014 paper shows the number of days a 30-year old male astronaut flying in a spaceship with 10 g/cm2 of aluminum shielding could go before hitting NASA-mandated radiation limits:

missionduration_strip

In the 1990s, the astronaut could spend 1000 days in interplanetary space. In 2014 … only 700 days. “That’s a huge change,” says Schwadron.

Galactic cosmic rays come from outside the solar system. They are a mixture of high-energy photons and sub-atomic particles accelerated toward Earth by supernova explosions and other violent events in the cosmos. Our first line of defense is the sun:  The sun’s magnetic field and solar wind combine to create a porous ‘shield’ that fends off cosmic rays attempting to enter the solar system. The shielding action of the sun is strongest during Solar Maximum and weakest during Solar Minimum–hence the 11-year rhythm of the mission duration plot above.

The problem is, as the authors note in their new paper, the shield is weakening: “Over the last decade, the solar wind has exhibited low densities and magnetic field strengths, representing anomalous states that have never been observed during the Space Age. As a result of this remarkably weak solar activity, we have also observed the highest fluxes of cosmic rays.”

Back in 2014, Schwadron et al used a leading model of solar activity to predict how bad cosmic rays would become during the next Solar Minimum, now expected in 2019-2020.  “Our previous work suggested a ∼ 20% increase of dose rates from one solar minimum to the next,” says Schwadron. “In fact, we now see that actual dose rates observed by CRaTER in the last 4 years exceed the predictions by ∼ 10%, showing that the radiation environment is worsening even more rapidly than we expected.” In this plot bright green data points show the recent excess:

excess_crater_strip

The data Schwadron et al have been analyzing come from CRaTER on the LRO spacecraft in orbit around the Moon, which is point-blank exposed to any cosmic radiation the sun allows to pass. Here on Earth, we have two additional lines of defense: the magnetic field and atmosphere of our planet. Both mitigate cosmic rays.

But even on Earth the increase is being felt. The students of Earth to Sky Calculus have been launching space weather balloons to the stratosphere almost weekly since 2015. Sensors onboard those balloons show a 13% increase in radiation (X-rays and gamma-rays) penetrating Earth’s atmosphere:

balloon_data_strip

X-rays and gamma-rays detected by these balloons are “secondary cosmic rays,” produced by the crash of primary cosmic rays into Earth’s upper atmosphere. They trace radiation percolating down toward our planet’s surface. The energy range of the sensors, 10 keV to 20 MeV, is similar to that of medical X-ray machines and airport security scanners.

How does this affect us? Cosmic rays penetrate commercial airlines, dosing passengers and flight crews so much that pilots are classified by the International Commission on Radiological Protection as occupational radiation workers. Some research shows that cosmic rays can seed clouds and trigger, potentially altering weather and climate. Furthermore, there are studies ( #1, #2, #3, #4) linking cosmic rays with cardiac arrhythmias in the general population.

Cosmic rays will intensify even more in the years ahead as the sun plunges toward what may be the deepest Solar Minimum in more than a century. Stay tuned for updates.

References:

Schwadron, N. A., et al (2014), Does the worsening galactic cosmic radiation environment observed by CRaTER preclude future manned deep space exploration?, Space Weather, 12, 622–632, doi:10.1002/2014SW001084.

Schwadron, N. A., et al (2018), Update on the worsening particle radiation environment observed by CRaTER and implications for future human deep-space exploration, Space Weather, doi: 10.1002/2017SW001803.

 

Earth’s Magnetic Field is Ringing Like a Bell

 Feb. 22, 2018: Today, a high speed solar wind stream is passing just south of Earth, making grazing contact with our planet’s magnetic field. This is causing something unusual to happen. Around the poles, Earth’s magnetic field has been ringing like a bell. Rob Stammes recorded the phenomenon from his magnetic observatory in Lofoton, Norway.

“Ths morning, the magnetic field around our observatory (as measured by ground currents) was swinging back an forth with a 100 second period,” says Stammes. “This very stable oscillation went on for more than an hour.”

This is quite different from what normally happens when a solar wind stream hits Earth’s magnetic field. Here is an example of Stammes’ recordings during a regular geomagnetic storm. Compared to the cacophany of a normal storm, this morning’s event was a sweet pure tone.

Researchers call these pure ultra-low frequency oscillations “pulsations continuous” (Pc). Pc waves have an energizing influence on particles in Earth’s inner magnetosphere because they resonate with the natural motion of particles around the geomagnetic field. This, in turn, can supercharge the aurora borealis.

Some of the energy injected by Pc waves is being observed right now in Sweden. “The auroras are going crazy!” reports Chad Blakley of Lights over Lapland, who roared out on his snowmobile to photograph the display:

“The lights were so impressive that I forgot that I was only wearing jeans before heading out! It may have been -25 degrees outside but it was worth 15 minutes in the cold to see a display that I will never forget,” says Blakley.

The effect of this solar wind stream may be likened to a person blowing across the top of a soda bottle, the glancing breath producing a nearly monochromatic waveform. “This is quite rare,” says Stammes. “Pulsating continuous signals like these are visible only 2 or 3 times a year.”

Stay tuned for more “ringing auroras” in the hours ahead. Free: Aurora Alerts

Realtime Aurora Photo Gallery

Rads on a Plane: The Data

Feb. 21, 2018: Many people think that only astronauts have to worry about cosmic radiation. Not so. Ordinary air travelers are exposed to cosmic rays, too. On a typical flight over the continental USA, radiation dose rates in economy class are more than 40 times higher than on the ground below. Cosmic rays penetrate the walls of aircraft with ease. This has  prompted the International Commission on Radiological Protection (ICRP) to classify pilots as occupational radiation workers–just like nuclear power plant engineers.

Since Jan. 2015, Spaceweather.com and the students of Earth to Sky Calculus have been monitoring cosmic rays in airplanes. Our method is simple: We board planes carrying the same cosmic ray payload we routinely fly to the stratosphere on space weather balloons. Inside the airplane we measure X-ray, gamma-ray and neutron dose rates along with GPS altitude, latitude and longitude

flightpaths
Above: Flight paths forming the basis of our aviation radiation study. 2015-2017

Three years after our first flight, our data set is impressive. We have 14,183 GPS-tagged radiation measurements collected during 67 flights over 2 oceans and 5 continents. We have spent 236.4 hours onboard planes taking data. If you accumulated that into a single flight, it would amount to 9.8 uninterrupted days on a plane.

This substantial data set is allowing us to explore how radiation varies with altitude around the globe. It’s not the same everywhere. The Arctic, for example, differs sharply from the equator, and there are interesting departures from “normal” near the South Atlantic Anomaly. We’re also discovering how Earth’s natural magnetism shields travelers from radiation: there’s a strong correlation in our data between dose rate and the geomagnetic field around the airplane.

Best of all, we can now predict dose rates for flights that haven’t even taken off yet. Using the data from 2015-2017, we’re building an empirical predictive model and actively testing it against new flights in 2018. Early results show that it works well over the continental USA, and we are beginning to check international flights, too.

Stay tuned for updates!

Long Dead NASA Spacecraft Wakes Up

Jan. 26, 2018:  Amateur astronomer Scott Tilley has a hobby: He hunts spy satellites. Using an S-band radio antenna in Roberts Creek, British Columbia, he regularly scans the skies for radio signals from classified objects orbiting Earth. Since he started 5 years ago, Tilley has bagged dozens of secret or unlisted satellites. “It’s a lot of fun,” he confesses.

Earlier this month, Tilley was hunting for Zuma–a secretive United States government satellite lost in a launch mishap on Jan. 8th–when a J-shaped curve appeared on his computer screen. “It was the signature of a lost satellite,” he says, “but it was not Zuma.”

In a stroke of good luck that has dizzied space scientists, Tilley found IMAGE, a NASA spacecraft that “died” more than 10 years ago.


An artist’s concept of IMAGE flying over Earth’s north pole.

Short for “Imager for Magnetopause-to-Aurora Global Exploration,” IMAGE was launched in 2000 on a flagship mission to monitor space weather. Mapping the ebb and flow of plasma around Earth, IMAGE was able to watch our planet’s magnetosphere respond almost like a living organism to blasts of solar activity, while its ultraviolet cameras took gorgeous pictures of Earth’s global auroras.

“It had capabilities that no other spacecraft could match–before or since,” says. Patricia Reiff, a member of the original IMAGE science team at Rice University.

IMAGE was in the 5th year of its extended mission on Dec. 18, 2005, when the spacecraft suddenly went silent. No one knows why, although suspicions have focused on a power controller for the spacecraft’s transponder, which might have temporarily failed.

The one hope was a reboot: When IMAGE’s solar-powered batteries drained to zero during a eclipse by the Earth, onboard systems could restart and begin transmitting again. “If revival occurs, the mission should be able to continue as before with no limitations,” noted NASA’s IMAGE Failure Review Board in their 2006 report.

A deep eclipse in 2007, however, failed to produce the desired result. “After that, we stopped listening,” says Reiff.


Radio signals from IMAGE, detected by Scott Tilley on Jan. 20, 2018. [more]

That is, until Scott Tilley started looking for Zuma. “When I saw the radio signature, I ran a program called STRF to identify it,” he says. Developed by Cees Bassa, a professional astronomer at the Netherlands Institute for Radio Astronomy, STRF treats Earth-orbiting satellites much like binary pulsars–deducing their orbital elements from the Doppler shifts of their radio signals. “The program immediately matched the orbit of the satellite I saw to IMAGE. It was that easy,” says Tilley.

Sometime between 2007 and 2018–no one knows when–IMAGE woke up and started talking. Now, NASA has to find a way to answer.

“The good news is, NASA is working on a recovery plan,” says Reiff. “UC Berkeley still has a ground station that was used for realtime tracking and control. They are scrambling to find the old software and see it they can get the bird to respond. Apparently there are data side lobes on the transmission, so that is a good sign.”

Researchers would love to have IMAGE back. The spacecraft has a unique Big Picture view of Earth’s magnetosphere and “its global-scale auroral imager would be fantastic for nowcasting space weather,” says Reiff. “Fingers crossed!!”

Blue Moon Lunar Eclipse

Jan. 25, 2018: On Wednesday, Jan. 31st, there’s going to be a “Blue Moon”–the second full Moon in a calendar month. People who go outside to look may see a different hue: bright orange. This Blue Moon is going to be eclipsed, swallowed by copper-colored shadow of Earth for more than an hour. The eclipse will be visible from Asia, Australia, and most of North America: visibility map.

EclipsetimesPST
Other time zones: UT, EST, CST, MST, PST, HST. Credit: Larry Koehn.

The bright orange color of the eclipse may be chalked up to volcanic activity–or rather, lack thereof. Atmospheric scientist Richard Keen from the University of Colorado explains:

“During a lunar eclipse, most of the light illuminating the Moon passes through Earth’s stratosphere where it is reddened by scattering,” he says. “If the stratosphere is loaded with dust from volcanic eruptions, the eclipse will be dark. The cataclysmic explosion of Tambora in 1815, for instance, turned the Moon into a dark, starless hole in sky during two subsequent eclipses.”

But Earth is experiencing a bit of a volcanic lull. We haven’t had a major volcanic blast since 1991 when Mt Pinatubo awoke from a 500 year slumber and sprayed ten billion cubic meters of ash, rock and debris into Earth’s atmosphere. Recent eruptions have been puny by comparison and have failed to make a dent on the stratosphere. To Keen, the interregnum means one thing: “This eclipse is going to be bright and beautiful.”

opticaldepth
From “Two Centuries of Volcanic Aerosols Derived from Lunar Eclipse Records” by R.  Keen

Keen studies lunar eclipses because of what they can tell us about Earth’s energy balance. A transparent stratosphere “lets the sunshine in” and actually helps warm the Earth below. “The lunar eclipse record indicates a clear stratosphere has contributed about 0.2 degrees to warming since the 1980s.”

“Mt. Pinatubo finished a 110-year episode of frequent major eruptions that began with Krakatau in 1883,” he says. “Since then, lunar eclipses have been relatively bright, and the Jan. 31st eclipse should be no exception.”

In the USA, the best time to look is during the hours before sunrise. Western states are favored: The Moon makes first contact with the core of Earth’s shadow at 3:48 am Pacific Time, kicking off the partial eclipse. Totality begins at 4:52 am PST as Earth’s shadow engulfs the lunar disk for more than an hour. “Maximum orange” is expected around 5:30 am PST. Easternmost parts of the USA will miss totality altogether.

“I welcome any and all reports on the brightness of this eclipse for use in my volcano-climate studies,” says Keen.  While actual brightness measurements (in magnitudes) made near mid-totality are most useful, I can also make use of Danjon-scale ratings. Please be sure to note the time, method, and instruments used in your reports.” Observations may be submitted here.

visibilitymap

The Pacific Radiation Bowl

Jan. 22, 2018: For years, Spaceweather.com and the students of Earth to Sky Calculus have been flying balloons to the stratosphere to monitor cosmic rays penetrating Earth’s atmosphere. Lately, we’ve been flying the same payloads onboard airplanes. We want to map Earth’s radiation environment at aviation altitudes where millions of people are routinely exposed to elevated levels of cosmic rays.

Recently we encountered an interesting feature in data taken over the Pacific Ocean: a “radiation bowl.” On Nov. 30th, 2017, Hervey Allen, a computer scientist at the University of Oregon, carried our radiation sensors onboard a commercial flight from San Francisco, California, to Auckland, New Zealand: map. As his plane cruised at a nearly constant altitude (35,000 ft) across the equator, radiation levels gracefully dipped, then recovered, in a bowl-shaped pattern:

equatorcrossing

map2

In one way, this beautiful curve is no surprise. We expect dose rates to reach a low point near the equator, because that is where Earth’s magnetic field provides the greatest shielding against cosmic rays. Interestingly, however, the low point is not directly above the equator. A parabolic curve fit to the data shows that the actual minimum occurred at 5.5 degrees N latitude.

Is Earth’s “radiation equator” offset from the geographic equator? Very likely it is. Earth’s magnetic field is tilted with respect to Earth’s spin axis and, moreover, there are many inhomogeneities in our planetary magnetic field that may create radiation zones of interest in unexpected places.

We are now planning additional trips across the equator to map the band of least radiation girdling our planet. In fact, we are working on a dataset now that includes an equator-crossing between the USA and Chile. Stay tuned for updates.