Solar Wind Summons “Steve”

May 21, 2017: During Saturday morning’s solar wind storm, photographer Harlan Thomas stationed himself among the Hoodoos in the badlands of Alberta, Canada. He hoped to catch a display of auroras. This is what he saw:

“Steve appeared!” says Thomas. “I photographed him behind the silhouettes of the Hoodoos alongside Jupiter and a green picket fence aurora.”

“Steve” is the purple arc bisecting the sky. For many years, northern sky watchers have reported this luminous form occasionally dancing among regular auroras. It was widely called a “proton arc” until researchers pointed out that protons probably had nothing to do with it. So members of the Alberta Aurora Chasers group gave it a new name: “Steve.”

No one fully understands the underlying physics of the purple ribbon. However, one of the European Space Agency’s Swarm satellites recently flew overhead while Steve was active, providing some clues.


This ESA video shows Swarm satellites orbiting above ground-based aurora imagers: more

“As the satellite flew straight though ‘Steve,’ data from the electric field instrument showed very clear changes,” reports Eric Donovan from the University of Calgary. “The temperature 300 km above Earth’s surface jumped by 3000°C and the data revealed a 25 km-wide ribbon of gas flowing westwards at about 6 km/s compared to a speed of about 10 m/s either side of the ribbon.”

Steve’s visit to Alberta on May 20, 2017, coincided with another exotic auroral form: the green “picket fence.” These vertical rays are thought to trace lines of magnetic force connecting Earth to space. Luminous green columns show where beams of energetic particles are being guided toward Earth’s upper atmosphere by magnetic fields.

Both Steve and the picket fence are filamentary structures associated with beams or ribbons of gas. Coincidence? Hardly. Pictures of the two phenomena show that they often appear together. Consider it another clue.

Realtime “Steve” Photo Gallery

“Steve” Sighted over Calgary

May 18, 2017: For years, northern sky watchers have occasionally spotted a mysterious ribbon of purple light dancing among the aurora borealis. It was widely called a “proton arc” until researchers pointed out that protons probably had nothing to do with it. So members of the Alberta Aurora Chasers group gave it a new name: “Steve.” Recent widespread reporting about Steve has led to even more sightings–and indeed he appeared just this week over Calgary:

“Steve hung out with me for about 15 minutes on May 17th,” reports photographer Harlan Thomas, who witnessed a spectacular display of auroras over Twisted Ponds. The lights appeared as Earth moved through a stream of fast-moving solar wind that briefly interacted with our planet two days ago.

Steve is still a mystery. No one fully understands the underlying physics of the ribbon.  However, one of the European Space Agency’s SWARM satellites recently flew overhead while Steve was active, providing some clues.

“As the satellite flew straight though Steve, data from the electric field instrument showed very clear changes” reports Eric Donovan from the University of Calgary. “The temperature 300 km above Earth’s surface jumped by 3000°C and the data revealed a 25 km-wide ribbon of gas flowing westwards at about 6 km/s compared to a speed of about 10 m/s either side of the ribbon.”

These clues, confirmed and supplemented by similar flybys in the future, may yet crack the mystery of this phenomenon. For now, Steve is unpredictable and may appear in the aurora gallery at any time. Stay tuned!

Realtime Aurora Photo Gallery

Anthropogenic Space Weather

May 18, 2017: Space weather can have a big effect on human society. Sometimes human society returns the favor. A new study entitled “Anthropogenic Space Weather” just published in Space Science Reviews outlines how human activity shapes the space around our planet. A prime example: Human radio transmissions form a bubble in space protecting us from “killer electrons.”

Co-author Phil Erickson of MIT’s Haystack Observatory explains: “As Van Allen discovered in the 1950s and 1960s, there are two radiation belts surrounding Earth with a ‘slot’ between them. Our research is focused on the the outer radiation belt, which contains electrons with energies of a million or more electron-volts. These ‘killer electrons’ have the potential to damage spacecraft, even causing permanent failures.”

During strong geomagnetic storms, the outer radiation belt expands, causing the killer electrons to approach Earth. But NASA’s Van Allen Probes, a pair of spacecraft sent to explore the radiation belts, found that something was stopping the particles from getting too close.

“The penetration of the outer belt stopped right at the same place as the edge of VLF strong transmissions from humans on the ground,” says Erickson. “These VLF transmissions penetrate seawater, so we use them to communicate with submarines. They also propagate upward along Earth’s magnetic field lines, forming a ‘bubble’ of VLF waves that reaches out to about 2.8 Earth-radii–the same spot where the ultra-relativistic electrons seem to stop.”

VLF radio waves clear the area of killer electrons “via a wave-particle gyro-resonance,” says Erickson. “Essentially, they are just the right frequency to scatter the particles into our atmosphere where their energy is safely absorbed.”

“Because powerful VLF transmitters have been operating since before the dawn of the Space Age, it is possible that we have never observed the radiation belts in their pristine, unperturbed state,” notes the team, which includes John Foster, a colleague of Erickson at MIT and a key leader of this research, along with Dan Baker at the University of Colorado Boulder.

Other anthropogenic effects on space weather include artificial radiation belts created by nuclear tests, high-frequency wave heating of the ionosphere, and cavities in Earth’s magnetotail formed by chemical release experiments. Download the complete paper here.

Cosmic Rays Intensify: May 2017

May 7, 2017: As the sunspot cycle declines, we expect cosmic rays to increase. Is this actually happening? The answer is “yes.” Spaceweather.com and the students of Earth to Sky Calculus have been monitoring radiation levels in the stratosphere with frequent high-altitude balloon flights over California. Here are the latest results, current as of May 6, 2017:

The data show cosmic ray levels intensifying with an approximately 13% increase since March 2015.

Cosmic rays are high-energy photons and subatomic particles accelerated in our direction by distant supernovas and other violent events in the Milky Way. Usually, cosmic rays are held at bay by the sun’s magnetic field, which envelops and protects all the planets in the Solar System. But the sun’s magnetic shield is weakening in 2017 as the solar cycle shifts from Solar Maximum to Solar Minimum. More and more cosmic rays are therefore reaching our planet.

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

The sensors we send to the stratosphere measure X-rays and gamma-rays, which are produced by the crash of primary cosmic rays into Earth’s atmosphere. The energy range of the sensors, 10 keV to 20 MeV, is similar to that of medical X-ray machines and airport security scanners.