CME Sweeps Aside Cosmic Rays

July 18,2017: On July 16th, a CME hit Earth’s magnetic field, sparking two days of geomagnetic storms and beautiful southern auroras. The solar storm cloud also swept aside some of the cosmic rays currently surrounding Earth. and the students of Earth to Sky Calculus launched a space weather balloon to the stratosphere hours after the CME arrived. We detected a 7% decrease in X-rays and gamma-rays (two tracers of secondary cosmic rays). Neutron monitors in the Arctic and Antarctic recorded similar decrements. For instance, these data from the Bartol Research Institute show a nearly 8% drop in cosmic ray neutrons reaching the South Pole:

This is called a “Forbush Decrease,” named after physicist Scott E. Forbush who first described it in the 20th century. Wherever CMEs go, cosmic rays are deflected by magnetic fields inside the solar storm clouds. As a result, when solar activity is high, cosmic radiation around Earth is relatively low–a yin-yang relationship that holds throughout all phases of the solar cycle.

Lately, cosmic rays around Earth have been intensifying as the solar cycle plunges toward minimum. The CME of July 16th reversed that trend–but only for a few days. Solar activity has returned to low levels and cosmic rays are on the rise again.

Why do we care about cosmic rays? For one thing, they penetrate commercial airlines, dosing passengers and flight crews so much 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.

Giant ‘ELVE’ Appears over Europe

On April 2nd, high above a thunderstorm in the Czech republic, an enormous ring of light appeared in the night sky. Using a low-light video camera, amateur astronomer Martin Popek of Nýdek photographed the 300 km-wide donut hovering near the edge of space:

“It appeared for just a split second alongside the constellation Orion” says Popek.

This is an example of an ELVE (Emissions of Light and Very Low Frequency Perturbations due to Electromagnetic Pulse Sources). First seen by cameras on the space shuttle in 1990, ELVEs appear when a pulse of electromagnetic radiation from cloud-to-ground lightning propagates up toward space and hits the base of Earth’s ionosphere. A faint ring of deep-red light marks the broad ‘spot’ where the EMP hits.

“For this to happen, the lightning needs to be very strong–typically 150-350 kilo-Ampères,” says Oscar van der Velde, a member of the Lightning Research Group at the Universitat Politècnica de Catalunya. “For comparison, normal cloud-to-ground flashes only reach 10-30 kA.”

ELVEs often appear alongside red sprites, which are also sparked by strong lightning. Indeed, Popek’s camera caught a cluster of sprites dancing nearby.

ELVEs are elusive–and that’s an understatement. Blinking in and out of existence in only 1/1000th of a second, they are completely invisible to the human eye. For comparison, red sprites tend to last for hundredths of a second and regular lightning can scintillate for a second or more. Their brevity explains why ELVEs are a more recent discovery than other lightning-related phenomenon. Learn more about the history and physics of ELVEs here and here.

Realtime Sprite Photo Gallery

Mystery of the Missing Noctilucent Clouds

 June 15, 2017: In late May 2017, observers in Europe began seeing electric-blue tendrils snaking over the western horizon at sunset. The summer season for noctilucent clouds (NLCs) was apparently beginning. Normally, the strange-looking clouds surge in visibility in the weeks immediately after their first sighting. This year, however, something mysterious happened. Instead of surging, the clouds vanished. During the first two weeks of June 2017, received ZERO images of NLCs — something that hasn’t happened in nearly 20 years.

Where did they go? Researchers have just figured it out: There’s been a “heat wave” in the polar mesosphere, a region in Earth’s upper atmosphere where NLCs form. Relatively warm temperatures have wiped out the clouds.

Lynn Harvey of the University of Colorado’s Laboratory for Atmospheric and Space Physics made the discovery using temperature data from the Microwave Limb Sounder onboard NASA’s Aura satellite. “In early May, the summer mesosphere was cooling down as usual, approaching the low temperatures required for NLCs,” she says. “But wouldn’t you know it? Right after May 21st the temperature stopped cooling over the pole! In fact, it warmed a degree or two over the next week. The warming resulted in 2017 being the WARMEST summer mesopause in the last decade.”

She is describing the red curve in this 10-year plot of polar mesospheric temperature trends:

Warm temperatures are an anathema to NLCs. The icy clouds form 83 km above Earth when the air temperature drops below 145 K (-128 C), allowing scarce water molecules to get together and crystallize on specks of meteor smoke. Even a couple of degrees of warming is enough to obliterate the fragile clouds.

“We don’t know why the mesosphere warmed up,” says Cora Randall, Professor and Chair of the University of Colorado Department of Atmospheric and Oceanic Sciences.  “It’s probably a complex process involving the propagation of atmospheric gravity waves, which affect the flow of air in the upper atmosphere. We’re looking into it.”

Meanwhile, the heat wave may be coming to an end. “In the last week, the north polar mesopause has started cooling again,” says Harvey. This means NLCs should soon return, bouncing back to normal as temperatures drop. High latitude sky watchers should be alert for electric-tendrils creeping out of the sunset in the nights ahead–and if you see anything, submit your pictures here!

Realtime Noctilucent Cloud Photo Gallery

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.” 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.

Neutrons on a Plane

March 18, 2017: Among researchers, it is well known that air travelers are exposed to cosmic rays. High-energy particles and photons from deep space penetrate Earth’s atmosphere and go right through the hulls of commercial aircraft. This has prompted the International Commission on Radiological Protection (ICRP) to classify pilots and flight attendants as occupational radiation workers.

Many studies of this problem focus on ionizing radiation such as x-rays and gamma-rays. On March 16th we turned the tables and measured neutrons instead. During a 12-hour flight from Stockholm to Los Angeles, and the students of Earth to Sky Calculus used bubble chambers to monitor neutron activity inside a Scandinavian Airlines jetliner.

In the photo above, taken 35,000 feet above Greenland, each bubble shows where a neutron passed through the chamber and vaporized a superheated droplet. By the time the long flight was over, we measured almost 20 uSv (microsieverts) of radiation from neutrons–similar to the dose from a panoramic X-ray at your dentist’s office. This confirms that neutrons are an important form of aviation radiation relevant to both air travelers and future space tourists.

Where do these neutrons come from? Mainly, they are secondary cosmic rays. When primary cosmic rays from deep space hit Earth’s atmosphere, they produce a spray of secondary particles including neutrons, protons, alpha particles, and other species. Cosmic ray neutrons can reach the ground; indeed, researchers routinely use neutron counters on Earth’s surface to monitor cosmic ray activity above the atmosphere. Now we’re doing the same thing onboard airplanes.

Earlier in the week, we flew these bubble chambers to the Arctic stratosphere using a space weather balloon. Interestingly, the 12-hour plane flight yielded ~6 times more neutrons than the shorter (2 hour) but far higher (97,000 ft) balloon flight to the stratosphere. What does it mean? We’re still analyzing the data and will have more insights to share in the days ahead. Stay tuned!

Arctic Space Weather Balloon Launch

March 3, 2017: is going to Sweden–and we’re taking a team of student researchers from Earth to Sky Calculus with us. For a week beginning on March 9th we plan to launch a series of space weather balloons equipped with cosmic ray sensors and cameras into the stratosphere above the Arctic Circle. At the same time, Earth to Sky launch teams in Chile and California will be sending up identical payloads, forming an intercontinental balloon network:

We’re doing this for three reasons:

1. To understand Earth’s changing radiation environment: Regular monitoring of the stratosphere over California shows that cosmic rays have intensified more than 10% since 2015.  Because of a recent decline in the solar cycle, more and more cosmic rays are reaching the inner solar system and penetrating the atmosphere of our planet. Earth’s magnetic field should protect us against these rays, but geomagnetism is weakening. Globally, Earth’s magnetic field has declined in strength by 10% since the 19th century with changes accelerating in recent years, according to measurements by Europe’s SWARM satellites. To understand Earth’s global response to these changes, we must launch balloons and sample radiation from widely-spaced locations.  The upcoming network launch will span three continents, more than 14,000 km of linear distance, and 90+ degrees of latitude.

Above: Satellite data show that Earth’s magnetic field is changing: full story.

2. To photograph the Northern Lights: We will be launching balloons from Abisko, Sweden, 250 km inside the Arctic Circle. Abisko is famous for spectacular auroras. One of our payloads will carry a low-light camera capable of photographing these lights from the stratosphere. Even at 120,000 feet, the balloon will be well below the auroras, but we will be a lot closer than any camera on the ground

3. To sample polar stratospheric clouds: During winter months, the stratosphere above the Arctic Circle sometimes fills with icy clouds so colorful, they are likened to the aurora borealis. Polar stratospheric clouds (PSCs) are a sign of extremely cold temperatures in the stratosphere and some types of PSCs are responsible for ozone destruction. Our space weather balloons can fly right through these clouds, sampling their temperature, pressure, and ambient levels of radiation.  We can also photograph them from the inside–a possible first!

Above: Polar stratospheric clouds over Kiruna, Sweden, on Feb. 14. Credit: Mia Stålnacke

Stay tuned for daily updates beginning March 9th.

“Daytime Auroras” … a.k.a. Polar Stratospheric Clouds

Feb. 15, 2017: On Feb. 13th, something amazing happened in the stratosphere over the Arctic Circle. Normally, the air 60,000+ feet above Earth’s surface is dry and utterly transparent.  On the eve of Valentine’s Day, however, the Arctic stratosphere filled with a gossamer haze of crystalline ice, and when sunlight hit the freezing crystals, the sky filled with clouds of intense iridescent color.

“Our guests referred to the clouds as ‘daytime auroras,'” reports Chad Blakley, who operates the Lights over Lapland tour guide service in Abisko, Sweden. One of them, Champ Cameron (@champcameron on Instagram), snapped this picture of the display:

“Champ was participating in our Sami And Reindeer Experience outside of Abisko yesterday afternoon,” explains Blakley. “The roads were very icy due to a freak rain storm and warm weather (+9 degrees C) so we nearly canceled the trip. But we heard that there were incredible clouds in the sky so we chose to brave the weather and push on.”

Good thing. They witnessed an exceptional display of polar stratospheric clouds (PSCs). PSCs are a sign of very cold temperatures in the stratosphere. For ice crystals to form in the normally arid stratosphere, temperatures must drop to around -85º C. So while it was strangely warm on the ground below, it was incredibly cold up above.

Longtime observers say PSCs are becoming more common and more intense. “I’ve been living here all my life (33 years),” says Mia Stålnacke of Kiruna, Sweden, who also photographed the colorful outbreak. “I definitely feel that these clouds are appearing more often then they used to. I remember seeing them a few times/year since I was a kid, but these last couple of years we’ve had them much more often–sometimes for almost a week straight. Others seem to feel the same way; I see local groups on Facebook flooded with photos of PSCs and comments on how often they’re appearing now.”

“Our bus driver, a longtime resident of the area, described it as the best PSC display he had ever seen,” relays Blakley. “We were overwhelmed by the natural beauty.” The clouds were so intense, they remained visible even after the sun set:

“We saw these clouds all day long, and they continued into the night,” says photographer Lars Lehnert of Abisko, Sweden. ” I’ve never seen anything quite like it.”

Once thought to be mere curiosities, some PSCs are now known to be associated with the destruction of ozone. Indeed, an ozone hole formed over the UK in Feb. 2016 following an outbreak of ozone-destroying Type 1 PSCs.

To investigate these clouds further, and the students of Earth to Sky Calculus will travel to Abisko Sweden for a week in March 2017.  We plan to launch a series of space weather balloons into the Arctic stratosphere, measuring temperature, air pressure, and ambient radiation.  If PSCs are present, our sensors will pass directly through them, and our cameras can photograph the colorful clouds at point blank range. Stay tuned!

Realtime PSC Photo Gallery