The sun is entering a deep Solar Minimum, and Earth's upper atmosphere is responding. Data from NASA's TIMED satellite show that the thermosphere (the uppermost layer of air around our planet) is cooling and shrinking, literally decreasing the radius of the atmosphere. If current trends continue, the thermosphere could set a Space Age record for cold in the months ahead: Full story.
The northern autumnal equinox is only a week away (23 September). 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 pours through the gaps to fuel bright displays of Northern Lights. It happened just last night in Rovaniemi, Finland:
"The auroras were totally awesome," says photographer Alexander Kuznetsov. "We weren't expecting a huge storm, yet this was the best display of the new season."
This is called 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. North and South partially cancel one another, opening a crack. 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 September is one of the most geomagnetically active months of the year–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. There's no danger to people on Earth. Our planet's atmosphere intercepts the rush of incoming particles with no harm done and a beautiful afterglow. Stay tuned for more Arctic lights as autumn approaches.
The Moon is about to take a bite out of the sun. On Saturday, August 11th, there will be a partial solar eclipse visible from locations around the Arctic Circle and across much of Asia. During the 3+ hour event, as much as 73% of the solar disk will be covered. Selected cities in the eclipse zone include Moscow (2.1% coverage), Oslo (4.8%), Raykjavik (20%), Tromso (29%), and Seoul (35%). www.spaceweather.com
GEOMAGNETIC STORM PREDICTED: NOAA forecasters say there is a 75% chance of moderately strong (G2-class) geomagnetic storms on Sept. 13th. That's when a CME hurled into space by a powerful X8-class solar flare on 10 September will likely deliver a glancing blow to Earth's magnetic field. The impact of the CME could be enhanced by a fast-moving solar wind stream, expected to arrive at about the same time. If the G2-storm materializes, auroras in the USA could appear as low as New York to Wisconsin to Washington state.
SOLAR RADIATION STORM AND GROUND LEVEL EVENT: On Sept. 10th, departing sunspot AR2673 erupted, producing a powerful X8-class solar flare. The explosion propelled a CME into space and accelerated a swarm of energetic protons toward Earth. Both are visible in this coronagraph movie from the Solar and Heliospheric Observatory (SOHO):
(go to http://spaceweather.com/ to watch animation)
The many specks in this movie are not stars--they are solar protons striking SOHO's digital camera. Almost two days later these protons are still streaming past our planet, causing a moderately strong (S2-class) solar radiation storm. The latest data from SOHO show an ongoing blizzard of digital "snow" in coronagraph images:
What made this flare so 'radioactive'? It has to do with the location of AR2673 at the time of the explosion. The sun's western limb is magnetically well-connected to Earth. Look at this diagram. Magnetic fields spiraling back from the blast site led directly to our planet, funneling these energetic protons Earthward.
Normally, solar radiation storms are held at bay by our planet's magnetic field and upper atmosphere. On Sept.10th, however, there was a "ground level event" (GLE). Neutron monitors in the Arctic, Antarctic, and several other high latitude locations detected a surge of particles reaching all the way down to Earth's surface:
The Bartol Research Institute's South Pole Neutron Monitor detected a GLE on Sept. 10th.
"In historical terms, this was a relatively small ground level event-- only about one thousandth as strong as the event of 23 Feb 1956, which is the largest measured," says Clive Dyer, a Visiting Professor at the University of Surrey Space Centre.
However, that does not mean the Sept.10th GLE was negligible. Dyer says that "passengers flying on high-latitude routes at 40,000 feet could have absorbed an extra 10 microSieverts of radiation. During the first hour of the GLE, the dose rate inside the aircraft during such a flight would have approximately doubled."
He also notes that the GLE could have caused minor upsets of onboard electronics and avionics, although nothing on the scale of the epic 1956 GLE, "which would be very challenging to modern systems."
"Since measurements began around 1942 there have now been 73 events detected by ground level radiation monitors," Dyer adds. "The Sept.10, 2017, event is far from the strongest, but it is of special interest because it demonstrates the need for continual vigilance even during Solar Minimum." www.spaceweather.com
On Sept. 6th at 12.02 UT, sunspot AR2673 unleashed a major X9.3-class solar flare--the strongest solar flare in more than a decade. X-rays and UV radiation from the blast ionized the top of Earth's atmosphere, causing a strong shortwave radio blackout over Europe, Africa and the Atlantic Ocean (blackout map). The explosion also produced a CME, shown here in a movie from NASA's STEREO-A spacecraft. (The fast moving star-like object in the STEREO-A movie is the planet Mercury.) NOAA analysts are still modeling the trajectory of the CME to determine whether or not it is Earth-directed.
Many readers are asking about the historic context of this event. How epic is it? Answer: This is a decade-class flare. A list of the most powerful solar flares recorded since 1976 ranks today's flare at #14, tied with a similar explosion in 1990. Compared to the iconic Carrington Event of 1859, or even the more recent Halloween storms of 2003, this event is relatively mild. Modern power grids, telecommunications, and other sun sensitive technologies should weather the storm with little difficulty.
On the other hand, sky watchers could see some fantastic auroras before the week is over. And ham radio operators will surely be noticing strange propagation effects as the sun exerts its influence on our planet's ionosphere.Stay tuned for updates.
Above: The extreme UV flash from today's X9-class flare. Credit: Solar Dynamics Observatory
The source of today's major flare is huge sunspot AR2673, shown here in a Sept. 5th photo taken by amateur astronomer Philippe Tosi of Nîmes, France:
How big is AR2673? An image of Earth has been inserted for scale. The largest of AR2673's dark cores are as wide as our entire planet, and they are surrounded by dozens of smaller cores as big as continents. Amateur astronomers with safely-filtered solar telescopes will have no trouble seeing this behemoth. Overarching the complex collection of spots is a tangled magnetic canopy that harbors energy for strong solar flares. Stay tuned for more explosions...
Only a few weeks ago, it seemed that the sun would be quiet and featureless when the Moon eclipsed it on Aug. 21st. Solar Minimum was in full swing. This weekend, however, the sun is welcoming the eclipse with a burst of renewed activity. "As the Moon approaches the sun, our nearest star is extending a friendly hand towards it," says Dave Eagle who sends this picture from Higham Ferrers, England:
"There is a huge prominence on the sun's eastern limb. If you are in the total eclipse path set your clock to greet this awesome spectacle on Monday," he says.
And that's just for starters. In addition, a remarkably-long sunspot group is sprawling across the solar disk. AR2671 stretches 140,000 miles from end to end, almost twice as wide as the planet Jupiter. Bill Hrudey sends this picture of the behemoth from the Cayman Islands:
Amateur astronomers watching the eclipse through safe solar telescopes will have no trouble seeing the rugged edge of the Moon cut across this impressive sunspot, eclipsing one dark core after another. If we're really lucky, the sunspot will explode. AR2671 has a 'beta-gamma' magnetic field that harbors energy for M-class solar flares. Free: Solar Flare Alerts
On Aug. 21, 2017, every square inch of the USA will experience a solar eclipse. In most places, the eclipse will be partial - that is, the Moon will cross the sun off-center, leaving a crescent shaped portion of the solar disk exposed. Is it really worth the trip to the path of totality when you can stay home and see the partial eclipse? Pulitzer prize winner Annie Dillard, who witnessed both types of eclipses in 1979, compared them as follows:
"A partial eclipse is very interesting. It bears almost no relation to a total eclipse. Seeing a partial eclipse bears the same relation to seeing a total eclipse as kissing a man does to marrying him, or as flying in an airplane does to falling out of an airplane."
Indeed, during the minutes of totality, the whole world changes. Saying that day turns into night barely scratches the surface of it. The shadow of the Moon lances down to Earth from a quarter million miles away. On one end is you; on the other end is a million square miles of dusty lunar terrain. You're connected, and you can feel the cold.
Image Credit & Copyright: Tunç Tezel (TWAN), Alkim Ün
Darkness inside the path of totality has an alien quality. Because the shadow is only 70 miles wide, you can see daylight at the edges even while you stand in the dark core. This distant scattered light produces a slight reddish glow and unusual shadow effects. Many birds stop singing, daytime flower blossoms begin to close as if for the night, and bees return to their hives.
"What you see in an eclipse is entirely different from what you know," says Dillard, whose brilliant essay "Total Eclipse" is a must-read for anyone deciding whether to stay home ... or have their minds blown.
What do Christmas Eve, Christmas, and Boxing Day 2016 have in common? They were days without sunspots. Throughout the holiday weekend, the face of the sun was completely blank, and the sun itself looked like a big orange Christmas ornament:
Including Dec. 24th, 25th and 26th, 2016 has had 31 'spotless days'--a whole month's worth. We haven't had this many blank suns in a single year since 2010 (51 days). This is a sign that the sunspot cycle is crashing toward a new Solar Minimum.
There are many misconceptions about Solar Minimum. One holds that auroras vanish when sunspots disappear. Christmas Day 2016 was proof that the opposite is true. Without a hint of a sunspot on the solar disk, intense auroras raged around the Arctic Circle on Dec. 25th. What caused the luminous outburst? An enormous hole in the sun's atmosphere directed a stream of solar wind toward Earth, sparking a week-long display that is still underway. Such atmospheric holes are common during Solar Minimum, which is a fine time to see Arctic auroras.
Many people think space weather becomes dull or stops altogether during Solar Minimum. In fact, space weather changes in interesting ways. For instance, as the extreme ultraviolet output of the sun decreases, the upper atmosphere of Earth cools and collapses. This allows space junk to accumulate around our planet. Also, the heliosphere shrinks, bringing interstellar space closer to Earth; galactic cosmic rays penetrate our atmosphere with relative ease. Yes, Solar Minimum is coming ... but it won't be dull.
Published on Dec 4, 2016http://www.QuakeWatch.net
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A strong G3-class geomagnetic storm is underway on Oct. 25th as Earth enters a stream of solar wind flowing from a coronal hole on the sun. First contact with the stream produced a magnificent outburst of auroras over Alaska. Marketa S. Murray sends this picture from Fairbanks AK:
"The storm finally hit," says Murray, "and the auroras were unbelievable."
More auroras are in the offing tonight as the solar wind is blowing faster than ~700 km/s. Around the Arctic Circle, the Northern Lights should be quite bright. Lesser displays could cross the Canadian border into the United States.
Updated: Sept. 29 2016 // Next Flight: Oct. 1, 2016
Sept. 20, 2016: Readers, thank you for your patience while we continue to develop this new section of Spaceweather.com. We've been working to streamline our data reduction, allowing us to post results from balloon flights much more rapidly, and we have developed a new data product, shown here:
This plot displays radiation measurements not only in the stratosphere, but also at aviation altitudes. Dose rates are expessed as multiples of sea level. For instance, we see that boarding a plane that flies at 25,000 feet exposes passengers to dose rates ~10x higher than sea level. At 40,000 feet, the multiplier is closer to 50x. These measurements are made by our usual cosmic ray payload as it passes through aviation altitudes en route to the stratosphere over California.
What is this all about? Approximately once a week, Spaceweather.com and the students of Earth to Sky Calculus fly space weather balloons to the stratosphere over California. These balloons are equipped with radiation sensors that detect cosmic rays, a surprisingly "down to Earth" form of space weather. Cosmic rays can seed clouds, trigger lightning, and penetrate commercial airplanes. Furthermore, there are studies ( #1, #2, #3, #4) linking cosmic rays with cardiac arrhythmias and sudden cardiac death in the general population. Our latest measurements show that cosmic rays are intensifying, with an increase of more than 12% since 2015:
Why are cosmic rays intensifying? The main reason is the sun. Solar storm clouds such as coronal mass ejections (CMEs) sweep aside cosmic rays when they pass by Earth. During Solar Maximum, CMEs are abundant and cosmic rays are held at bay. Now, however, the solar cycle is swinging toward Solar Minimum, allowing cosmic rays to return. Another reason could be the weakening of Earth's magnetic field, which helps protect us from deep-space radiation.
The radiation sensors onboard our helium balloons detect X-rays and gamma-rays in the energy range 10 keV to 20 MeV. These energies span the range of medical X-ray machines and airport security scanners.
The data points in the graph above correspond to the peak of the Reneger-Pfotzer maximum, which lies about 67,000 feet above central California. When cosmic rays crash into Earth's atmosphere, they produce a spray of secondary particles that is most intense at the entrance to the stratosphere. Physicists Eric Reneger and Georg Pfotzer discovered the maximum using balloons in the 1930s and it is what we are measuring today.
In a surprising development, NASA has regained contact with the STEREO-B spacecraft after two years of silence. STEREO-B, which can see the farside of the sun, went quiet in 2014 after mission controllers tested a communications reset procedure. Unfortunately, STEREO-B failed the test. Since then, NASA has regularly attempted to regain contact using the Deep Space Network. On Aug. 21st, they succeeded, managing to receive a downlink carrier for several hours. In the days and weeks ahead, engineers will take steps to assess the health of STEREO-B and return it to service.
Something interesting is happening on the sun. On June 3rd the sunspot number dropped to 0, and the solar disk is still blank on June 5th. Latest images from NASA's Solar Dynamics Observatory reveal no significant dark cores:
What does this mean? The solar cycle is like a pendulum, swinging back and forth between periods of high and low sunspot number every 11 years. Today's blank sun is a sign that the pendulum is swinging toward low sunspot numbers. In other words, Solar Minimum is coming.
The spotless state of today's sun is just temporary. Underneath the visible surface of the sun, the solar dynamo is still churning out knots of magnetism that will soon bob to the surface to make new sunspots. The current solar cycle is not finished. It is, however, rapidly waning.
Forecasters expect the next Solar Minimum to arrive in 2019-2020. Between now and then, there will be lots of spotless suns. At first, the blank stretches will be measured in days; later in weeks and months. Don't expect space weather to grow quiet, however. Solar Minimum brings many interesting changes. For instance, as the extreme ultraviolet output of the sun decreases, the upper atmosphere of Earth cools and collapses. This allows space junk to accumulate around our planet. Also, the heliosphere shrinks, bringing interstellar space closer to Earth. Galactic cosmic rays penetrate the inner solar system with relative ease. Indeed, a cosmic ray surge is already underway. Goodbye sunspots, hello deep-space radiation!
It begins with a sneeze. Pollen floating through the air tickles your nose, and your body responds by expelling the allergen. Gesundheit! When the paroxysm subsides, look up at the sky. The same pollen that makes you sneeze can also make beautiful coronas around the sun, like this one photographed on June 1st by Vesa Vauhkonen of Rautalampi, Finland:
"Pine is strongly flowering now in middle Finland, and the coronas have been quite impressive over the past few days," says Vauhkonen. "Pollen is everywhere--not only in noses and eyes, but also around the setting sun."
Atmospheric optics expert Les Cowley explains the phenonenon: "Coronas are produced when light waves scatter from the outsides of small particles. Tiny droplets of water in clouds make most coronas, but opaque equal-sized pollen grains do even better. They make small but very colorful multi-ringed coronas."
"Unlike water droplets, pollens are non-spherical--and this adds to their magic," he continues. "Many have air sacs to help carry them in the wind. These align the grains to give beautiful elliptical coronas with bright spots." This is why Vauhkonen's pollen corona looks the way it does.
As northern spring turns into summer, pollen coronas become increasingly common. Look for them the next time your nose feels a tickle. www.spaceweather.com
Venus is about to pass directly behind the sun, an event astronomers call "superior conjunction." Coronagraphs onboard the Solar and Heliospheric Observatory (SOHO) are monitoring Venus as it disappears into the glare:
On June 7th, Venus will be at superior conjunction--a wonderful sight if only we could see it.
Like the Moon, Venus has phases and on June 7th it will be gloriously full. The entire hemisphere facing Earth will be illuminated. Venus's acid-laced clouds are terrific reflectors and a full Venus would surely be visible in broad daylight, an intense pinprick of light in the blue sky.
Venus's passage behind the sun marks an important transition. Earlier this year, Venus was a "morning star." After it emerges from behind the sun, it will become an "evening star" later in June. www.spaceweather.com
This section is for interesting items which are brought to my attention but which do not merit a separate article.
I welcome your comments, questions or suggestions on any topics you wish to contribute to this section.