A New Source of Space Radiation

August 9, 2019: Astronauts are surrounded by danger: hard vacuum, solar flares, cosmic rays. Researchers from UCLA have just added a new item to the list. Earth itself.

“A natural particle accelerator only 40,000 miles above Earth’s surface is producing ‘killer electrons’ moving close to the speed of light,” says Terry Liu, a newly-minted PhD who studied the phenomenon as part of his thesis with UCLA Prof. Vassilis Angelopoulos.

This means that astronauts leaving Earth for Mars could be peppered by radiation coming at them from behind–from the direction of their own home planet.

earthrise_crop

NASA’s THEMIS spacecraft ran across the particles in 2008 not far from the place where the solar wind slams into Earth’s magnetic field. Researchers have long known that shock waves at that location could accelerate particles to high energies–but not this high. The particles coming out of the Earth-solar wind interface have energies up to 100,000 electron volts, ten times greater than previously expected.

How is this possible? Liu found the answer using THEMIS data and computer simulations of the sun-Earth interface. When the solar wind meets Earth, it forms a shock wave around Earth’s magnetic field, shaped like the bow waves that form ahead of a boat moving through water. Within this “bow shock” immense stores of energy can be abruptly released akin to the sonic boom of an airplane.

Liu found that some electrons are shocked not just once, but twice or more, undergoing mirror-like reflections within the bow shock that build energy to unexpected levels. Most of the boosted particles shoot back into space away from Earth.

magnetosphere2

Above: Terry Liu created this diagram showing the location of the natural particle accelerator and how it spews radiation into space.

“Similar particles have been detected near Saturn, suggesting that the process is at work there as well,” says Liu.

“Indeed,” adds Angelopoulos, “this type of particle acceleration could be happening throughout the cosmos–from supernovas to solar storms–wherever a supersonic wind hits a barrier such as Earth’s magnetosphere.”

Meanwhile, back home, Earth-orbiting satellites and departing astronauts have a new source of radiation to contend with. It’s right over their shoulder.

Read the original research at Science Advances.

Raikoke Sunsets

Aug. 4, 2019: Over the weekend in DeSoto, Kansas, something strange happened to the sunset: It turned purple. “On Saturday night, I photographed a large dome of pinkish-purple light,” reports Doug Zubenel. “Strong crepuscular rays were also visible.”


Photo credit: Doug Zubenel of DeSoto, Kansas. August 3, 2019.

Purple sunsets are a sign of volcanic activity. Fine volcanic aerosols in the stratosphere scatter blue light which, when mixed with ordinary sunset red, produces a violet hue.

But which volcano? The answer is probably Raikoke, a volcano in the Kuril islands which erupted with such force on June 22, 2019, that it was seen from the International Space Station. NASA satellites confirm that aerosols from Raikoke reached the stratosphere and they have been circulating around the Northern Hemisphere ever since.

A similar eruption occurred 11 years ago, in Aug. 2008, when Alaska’s Kasatochi volcano spewed sulfurous gases into the stratosphere. For months sky watchers witnessed strange sunsets whenever a plume of Kasatochi’s emissions drifted overhead. The same thing, apparently, is happening now thanks to Raikoke.


Photo credit: Heiko Ulbricht in the Zittau Mountains of southeastern Germany. July 26, 2019.

Volcanic sunsets have also been seen in Halifax, Nova Scotia; in the Zittau Mountains of Germany; in Joshua Tree, California; in Orange, California.

Purple isn’t the only thing to look for, says atmospheric optics expert Les Cowley. In addition, he advises, sky watchers should “be alert for a very bright yellow twilight arch, fine cloud structure in the arch seen through binoculars, and long diffuse rays and shadows.”

Realtime Space Weather Photo Gallery
Free: Spaceweather.com Newsletter

Cosmic Ray Update: New Results from the Moon

July 16, 2019: Note to astronauts: 2019 is not a good year to fly into deep space. In fact, it’s shaping up to be one of the worst of the Space Age.

The reason is, the solar cycle. One of the deepest Solar Minima of the past century is underway now. As the sun’s magnetic field weakens, cosmic rays from deep space are flooding into the solar system, posing potential health risks to astronauts.

NASA is monitoring the situation with a radiation sensor in lunar orbit. The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) has been circling the Moon on NASA’s Lunar Reconnaissance Orbiter spacecraft since 2009. Researchers have just published a paper in the journal Space Weather describing CRaTER’s latest findings.

lro

Above: An artist’s concept of Lunar Reconnaissance Orbiter.

“The overall decrease in solar activity in this period has led to an increased flux of energetic particles, to levels that are approaching those observed during the previous solar minimum in 2009/2010, which was the deepest minimum of the Space Age,” write the authors, led by Cary Zeitlin of NASA’s Johnson Space Flight Center. “The data have implications for human exploration of deep space.”

This always happens during Solar Minimum. As solar activity goes down, cosmic rays go up. The last two Solar Minima have been unusually deep, leading to high cosmic ray fluxes in 2008-2010 and again in 2018-2019. These are the worst years since humans first left Earth in the 1960s.

“It’s a bit counterintuitive,” says one of the authors, Nathan Schwadron, a space physicist at the University of New Hampshire. “Solar Minimum may actually be more dangerous than Solar Maximum.”

In their paper, Zeitlin, Schwadron and co-authors describe an interesting experiment by NASA that highlights the relative peril of solar flares vs. cosmic rays. In 2011, NASA launched the Curiosity rover to Mars. Inside its spacecraft, the rover was protected by about as much shielding (20 gm/cm^2) as a human astronaut would have. A radiation sensor tucked inside kept track of Curiosity’s exposure.

The results were surprising. During the 9-month journey to Mars, radiation from solar flares (including the strongest flare of the previous solar cycle) accounted for only about 5% of Curiosity’s total dose. The remaining 95% came from cosmic rays.

Why the imbalance? “Solar flares of the size we’ve seen during the Space Age can be largely mitigated by achievable depths of spacecraft shielding(1),” explains Zeitlin. “We can’t stop the highest energy cosmic rays, however. They penetrate the walls of any spacecraft.”

Proton_F180_red-1_crop

Above: Since 2015, the flux of cosmic rays at the Moon has nearly doubled. Another plot shows the complete CRaTER record starting in 2010.

Solar flares are still a concern. If an astronaut were caught outside on EVA during an intense, unexpected flare, acute effects could include vomiting, fatigue, and low blood counts. A quick return to Earth might be required for medical care. Cosmic rays are more insidious, acting slowly, with maladies such as cancer or heart disease showing up years after the exposure.

As 2019 unfolds, Solar Minimum appears to still be deepening. Cosmic rays haven’t quite broken the Space Age record set in 2009-2010, but they’re getting close, only percentage points from the highest values CRaTER has ever recorded.

“No one can predict what will happen next,” says Schwadron. “However, the situation speaks for itself: We are experiencing a period of unusually weak solar cycles. We have to be prepared for strong cosmic rays.”

END NOTES:

(1) According to Zeitlin, “achievable” shielding depths will be at least 20 to 30 gm/cm^2. “Vehicles carrying humans into deep space will likely have storm shelters that will provide this much shielding or more, and that would indeed be sufficient – even for an event like the great solar flare of August 1972 during the Apollo program – to keep the accumulated dose below the 30-day limit.”

REFERENCE:

“Update on Galactic Cosmic Ray Integral Flux Measurements in Lunar Orbit With CRaTER”, by C. Zeitlin, N. A. Schwadron, H. E. Spence, A. P. Jordan, M. D. Looper, J. Wilson, J. E. Mazur, L. W. Townsend. https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019SW002223

A Sunspot from the Next Solar Cycle

July 8, 2019: Solar Cycle 25 is coming to life. For the second time this month, a sunspot from the next solar cycle has emerged in the sun’s southern hemisphere. Numbered “AR2744”, it is inset in this magnetic map of the sun’s surface from NASA’s Solar Dynamics Observatory:

How do we know this sunspot belongs to Solar Cycle 25? 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. AR2744 is therefore a member of Solar Cycle 25.

Solar cycles always mix together at their boundaries. Right now we are experiencing the tail end of decaying Solar Cycle 24. AR2744 shows that we are simultaneously experiencing the first stirrings of Solar Cycle 25. The transition between Solar Cycle 24 and Solar Cycle 25 is underway.

Shortlived “ephemeral sunspots” belonging to Solar Cycle 25 have already been reported on Dec. 20, 2016; April 8, 2018; Nov. 17, 2018; May 28, 2019 and July 1, 2019. Today’s sunspot is more important than those earlier examples because it has lasted long enough to receive a numerical designation: AR2744. Record-keepers will likely mark this as the first official sunspot of Solar Cycle 25.

This development 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. AR2744 is an important sign, however, that the next solar cycle is approaching.

Realtime Space Weather Photo Gallery
Free: Spaceweather.com Newsletter

Sunset Solar Eclipse

July 1, 2019: Residents of Chile and Argentina are about to witness a rare total eclipse of the sun. On July 2, 2019, the new Moon will pass across the solar disk, creating a black hole in the sky just before sunset in the two South American countries. This animated map, created by space artist Larry Koehn, includes a local timetable of events:

mp_strip2

The path of totality cuts across ESO’s La Silla Observatory in Chile and barely misses the center of Buenos Aires in Argentina. The Moon’s elongated sunset shadow will swallow observers for 1 to 2 minutes depending on their exact location.

Outside the path of totality, the eclipse is partial with significant coverage in large cities such as Santiago, Chile (93%); Montevideo, Uruguay (94%); La Paz, Bolivia (63%); and Lima, Peru (54%). During the partial phase of the eclipse, the sun looks like a crescent, and it casts crescent-shaped shadows on the ground. South Americans should look for them underneath the canopies of leafy trees. Using safe eclipse glasses, it is possible to view the crescent sun directly.

The sun and Moon align for an eclipse once or twice every year. Aligning directly over a major observatory, however, is very rare. This video shows what the eclipse will look like over La Silla:

La Silla is home to some of the world’s biggest telescopes and many skilled observers. Observatory staff will host more than a thousand members of the public in a viewing party among the telescope domes. A live high-definition webcast of the eclipse will be available on ESO’s website and on ESO’s Youtube Channel. The action begins on Tuesday, July 2nd. Stay tuned!

More live webcasts: from Chile; from Argentina; from La Silla.

Realtime Solar Eclipse Photo Gallery
Free: Spaceweather.com Newsletter

Nuke Sensors Detect Asteroid Explosion

June 25, 2019: On June 22nd at 21:25 UT, a small asteroid entered Earth’s atmosphere and exploded in broad daylight south of Puerto Rico. Airwaves recorded by the Comprehensive Nuclear Test Ban Treaty Organization’s infrasound station in Bermuda pegged the blast energy between 3 and 5 kilotons of TNT–a fraction of a WW II atomic bomb. The explosion was clearly visible in images from NOAA’s GOES-16 weather satellite:

bolide_strip

This movie combines data from GOES-16’s Global Lightning Mapper and water vapor infrared spectrometer

Meteor expert Peter Brown of the University of Western Ontario says the infrasound signal is consistent with a “small multi-meter sized near-Earth asteroid.” According to data compiled by NASA’s Center for Near Earth Object Studies, asteroids of this size and energy hit Earth’s atmosphere about once a year. That means it’s rare–but not exceptionally so.

The asteroid fragmented as it ripped through the atmosphere. This infrared image from the GOES-16 satellite shows the space rock splitting into at least 3 pieces:

william_straka_image2

Many more fragments undoubtedly sprayed from the explosion, but the resulting meteorites are now at the bottom of the Caribbean or (in the case of dust-sized debris) floating on the sea surface. Samples would be very difficult to recover.

Earth is currently approaching the Taurid Swarm–a stream of rocky debris associated with the Tunguska Impact of 1908. Astronomers are eager for the close encounter, which begins in late June, so they can peer inside the swarm in search of dangerous asteroids. This fireball, however, is not a Taurid.

“Based on a preliminary orbit for the fireball, it does not appear to be part of the Taurid swarm,” says Paul Weigert of the University of Western Ontario. “Its orbit is typical of near-Earth asteroids which have escaped from the asteroid belt.”

UPDATE: This asteroid may have been discovered shortly before it struck by an Atlas Project Survey telescope: more.

Realtime Space Weather Photo Gallery
Free: Spaceweather.com Newsletter

Extreme Noctilucent Clouds over Europe

June 21, 2019: What do you get when you mix the summer solstice with one of the deepest Solar Minima in a century? Extreme noctilucent clouds.

“On June 21st, at least 80% to 90% of our sky was covered by bright electric-blue waves,” reports Jacob Kuiper of Steenwijk, The Netherlands. “It was unbelievable, so bright and vast. For sure, this was the most extreme display I have seen in 35 years of observing NLCs.”

During the outburst, Spaceweather.com received pictures from almost every country in Europe as far south as Italy. The clouds were even visible in downtown Paris:

“I’ve been waiting 10 years to see these clouds in Paris,” says photographer Sylvain Weiller. “Finally, the NLCs are back!”

NLCs are Earth’s highest clouds. Seeded by meteoroids, they float at the edge of space more than 80 km above the planet’s surface. The clouds are very cold and filled with tiny ice crystals. When sunbeams hit those crystals, they glow electric-blue.

This close-up photo taken by Sebastian Voltmer of Spicheren, France, shows the clouds’ tell-tale wave structure:

This summer, extra moisture in the mesosphere has super-charged noctilucent clouds, allowing them to be sighted as far south as Rome, Italy; Los Angeles, California; and Paris, France. No one can predict exactly when they will appear. Tonight could be the night where you live.

Observing tips: Look west 30 to 60 minutes after sunset (or before sunrise) when the sun is just below the horizon. If you see luminous blue-white tendrils spreading across the sky, you may have spotted a noctilucent cloud.

Realtime Noctilucent Cloud Photo Gallery
Free:
Spaceweather.com Newsletter

The Sun is so Blank, It Looks Like a Billiard Ball

June 21, 2019: The sun is blank–really blank. No sunspots have appeared for the past 34+ days, giving the sun the appearance of a giant orange billiard ball. This is a sign that Solar Minimum is underway. Earlier this year, a panel of experts from NOAA and NASA predicted that the solar cycle would reach its nadir sometime between July 2019 and Sept 2020. The current stretch of spotless suns is consistent with their forecast.


Above: The sun on June 21, 2019. Credit: NASA’s Solar Dynamics Observatory

What happens when sunspots vanish? For one thing, solar flares stop happening. No big explosions means no shortwave radio blackouts and fewer geomagnetic storms. Also, the sun dims. Sunspots are sources of extreme ultraviolet radiation (EUV). Without sunspots, EUV levels decrease, causing Earth’s upper atmosphere to cool and contract. Satellites and space junk stay in orbit longer as aerodynamic drag subsides.

During this phase of the solar cycle, the solar wind slows and the sun’s magnetic field weakens–shields down! This allows extra cosmic rays from deep space to penetrate the solar system. Indeed, recent high altitude balloon flights show increased radiation in Earth’s atmosphere. Extra cosmic rays can trigger lightning, alter the electro-chemistry of the upper atmosphere, and boost dose rates on commercial airplane flights.

Solar Minimum won’t last forever. Forecasters expect sunspot numbers to increase after 2019-2020, climaxing in a new Solar Maximum around 2023-2026.  Meanwhile, stay tuned for more blank suns.

Realtime Space Weather Photo Gallery
Free: Spaceweather.com Newsletter

A Giant Palm Tree Sprite in Texas

June 21, 2019: Last night in Texas, a flurry of red sprites exploded from the top of a powerful thunderstorm. One of the the red forms was so tall and bright, people saw it 200 miles away in Oklahoma. “My boys and I saw it with our unaided eyes,” reports Paul Smith, who photographed the event from the shores of Lake Thunderbird, OK. This may be the first time that a sprite’s reflection has been captured in water:

Naked-eye sightings of sprites are rare, mainly because they are so fleeting. But this one left an impression. “My eleven-year-old son Thomas described it as a ‘huge orange-y-brown flash of lines high in the sky,'” says Smith. “My seven-year-old James just exclaimed ‘what the heck was that?'”

At first glance, Smith’s capture resembles a Gigantic Jet–that is, a type of “sprite on steroids.” But lightning expert Oscar van der Velde of the Universitat Politècnica de Catalunya thinks it may be something else:

“In early days of sprite research, they were called ‘palm trees’ by researchers from the University of Alaska,” van der Velde explains. “It is, basically, a bushy group of red sprites on top, with a secondary purple discharge hanging below. These types of events are quite rare. You need a big, active mesoscale convective system to produce them.”

Palm tree sprites are a topic of cutting edge research. “We haven’t even been able to confirm that they indeed originate from the thundercloud,” says van der Velde.

“Last night was so much fun,” adds Smith. “In addition to the sprites, my son Thomas photographed Jupiter and our Moon with the Nikon coolpix 80x zoom camera. We also saw a nice bolide exploding over the storms. The kid’s reactions were priceless.”

Realtime Sprite Photo Gallery
Free:
Spaceweather.com Newsletter

Mysterious Moisture in the Mesosphere

June 19, 2019: The 2019 season for noctilucent clouds (NLCs) has been remarkable, maybe the best ever, with NLCs appearing as far south as Los Angeles CA and Albuquerque NM. What’s going on? Researchers aren’t sure, but Lynn Harvey of the University of Colorado’s Laboratory for Atmospheric and Space Physics has just found an important clue.

“The mesosphere is quite wet,” she says. “Water vapor concentrations are at their highest levels for the past 12 years.”

electricblue

Noctilucent clouds over Piwnice, Poland, on June 18th. Credit: Piotr Majewski

Noctilucent clouds form when summertime wisps of water vapor rise to the top of the atmosphere. Water molecules stick to specks of meteor smoke, gathering into icy clouds that glow electric blue when they are hit by high altitude sunlight.

When noctilucent clouds began appearing at unusually low latitudes in early June, Harvey took a look at data from NASA’s Microwave Limb Sounder–a satellite-based sensor that can measure water in the upper atmosphere. Her results are shown in the animated plot below.

“The red line is 2019, while other colors trace previous years,” explains Harvey. “The plot cycles from low to high latitudes,” showing a wave of moisture in the mesosphere.

It’s a veritable tidal wave. Water vapor concentrations at lower latitudes (35 to 45 N) have nearly doubled their normal values, providing a surplus of H2O molecules for noctilucent clouds. Researchers aren’t sure where the water is coming from, though.

Planetary wave activity could be transporting cold air and high water vapor to the ‘noctilucent zone,'” speculates James Russell of Hampton University’s Center for Atmospheric Sciences. “We’ve seen this happen before during mid-latitude outbreaks of noctilucent clouds.”

The solar cycle may be helping, too. Right now a deep Solar Minimum is underway. Ultraviolet radiation that would normally destroy water in the mesosphere is at low ebb.

Ivo-Dinsbergs-_MG_0921_1560855825

Noctilucent clouds over Riga, Latvia,on June 18th. Credit: Ivo Dinsbergs

The wave appears to be breaking. “As we enter the 3rd week of June, the water has stopped increasing,” notes Harvey. “Poleward of 70N the water content has been dropping for a few weeks, and right around the north pole it’s getting quite dry. At mid-latitudes (35-65N), water content is still high, but it’s leveling off.”

No one knows what will happen next. Another wave could bring renewed sightings of NLCs at low latitudes. Or conditions could return to normal, restoring the clouds to their usual habitat near the Arctic Circle.  Says Russell, “this all points to mysteries of the atmosphere that have not been solved.” Stay tuned!

Realtime Noctilucent Cloud Photo Gallery
Free:
Spaceweather.com Newsletter