A minor interplanetary shock wave hit Earth on May 26th at approximately 22:00 UT. The CME-like disturbance was unexpected. It caused the density of the solar wind around Earth to abruptly quadruple, while the interplanetary magnetic field doubled in strength. Minor geomagnetic storms are possible on May 27th as our planet passes through the shock wave's wake.
Friday night (April 5th) in Norway, researchers at the Andøya Space Center launched two sounding rockets into a minor geomagnetic storm. The results were out of this world. Aurora tour guide Kim Hartviksen photographed glowing blobs of blue and purple caused by the rockets dumping chemical powders into the storm:
Photo credit: Kim Hartviksen of Aurora Addicts
"Residents for hundreds of miles were taken by surprise by these strange lights, which prompted calls to the police and 'The aliens are coming!' hysteria!" says Chris Nation who runs the Aurora Addicts guiding service.
When the night began, Nation, Hartviksen, and their clients were treated to a display of auroras, ignited by a stream of solar wind buffeting Earth's magnetic field. "As the auroras started to ebb away, our friends at Andøya launched their rockets into the fading lights," says Nation. "The show began anew as the rockets released their payload into the upper atmosphere."
An automated webcam operated by Chad Blakely of Lights over Lapland in Abisko, Sweden, caught the first puffs of powder emerging from the rockets. "It looked like an invasion of UFOs," says Blakley.
"Soon the glowing blobs evolved into more complicated structures--like two giant squid dancing in the northern sky with an impressive aurora display as its backdrop," decribes Blakley. "Our webcam has been taking a picture every five minutes for nearly 10 years. These images are by far the most exciting I've ever seen it record."
The name of the sounding rocket mission is AZURE--short for Auroral Zone Upwelling Rocket Experiment. Its goal is to measure winds and currents in the ionosphere, a electrically-charged layer of the Earth's atmosphere where auroras appear. Specifically, the researchers are interested in discovering how auroral energy might percolate down toward Earth to influence the lower atmosphere.
The twin rockets deployed two chemical tracers: trimethyl aluminum (TMA) and a barium/strontium mixture. These mixtures create colorful clouds that allow researchers to visually track the flow of neutral and charged particles, respectively. According to NASA, which funded the mission, the chemicals pose no hazard to residents in the region.
Update--a movie! "Here is my realtime video of the surprise rocket launch last night from NASA/ASC," reports Ole Salomonsen of Tromsø, Norway. "I was shocked when I saw this in the night sky facing north, I was not aware of the launch.
During the late hours of March 16th, a crack opened in Earth's magnetic field - not a big one, but big enough to cause a G1-class geomagnetic storm. Markus Varik witnessed the resulting auroras over Tromsø, Norway:
"It sure felt like the sky was falling on the ground," says Varik. "Just look at the town below the lights--like a mote of dust in space!"
This storm was not predicted, yet it comes as no surprise. The vernal equinox is only a few days away, and at this time of year cracks often form in Earth's magnetic field. Solar wind can pour through the gaps to fuel bright displays of Arctic lights.
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."
Northern spring is just around the corner. Stay tuned for green. Aurora Alerts: SMS text, email.
When a stream of solar wind hits Earth's magnetic field, magnetometers around the Arctic Circle normally go a bit haywire, with their needles swinging chaotically as the buffeting ensues. Rob Stammes of the Polarlightcenter, a magnetic observatory in Norway, sees such disordered behavior all the time. But on Nov. 18th something quite different happened. The solar wind produced a pure sine wave:
"A very stable ~15 second magnetic oscillation appeared in my recordings, and lasted for several hours," he says. "The magnetic field was swinging back and forth by 0.06 degrees, peak to peak."
Imagine blowing across a piece of paper, making it flutter with your breath. The solar wind can have a similar effect Earth's magnetic field. The waves Stammes recorded are essentially flutters propagating down the flanks of our planet's magnetosphere excited by the breath of the sun. Researchers call them "pulsations continuous" -- or "Pc" for short..
"A sensitive magnetometer is required to record these waves," says Stammes. "I use a mechanical magnetometer with bar magnets suspended from a special wire. LEDs and light detectors in an isolated dark box record the motion of the magnets, while vanes in oil damp out non-magnetic interference."
Pc waves are classified into 5 types depending on their period. The Nov. 18th waves fall into category Pc3. Researchers have found that Pc3 waves sometimes flow around Earth's magnetic field and cause a "tearing instability" in our planet's magnetic tail. This, in turn, sets the stage for an explosion as magnetic fields in the tail reconnect.
A quartet of NASA spacecraft recently flew through just such an explosion. Last week, researchers from the University of New Hampshire reported that four Magnetospheric Multiscale (MMS) spacecraft spent several seconds inside a magnetic reconnection event as they were orbiting through Earth's magnetic tail. Sensors on the spacecraft recorded jets of high energy particles emerging from the blast site. One jet was aimed squarely at Earth and probably sparked auroras when it hit the upper atmosphere.
Stammes has recorded many Pc waves in the past, "but this is the first time I have detected category Pc3," he says. "This was a very rare episode indeed."
Last weekend, Nov. 10th, a stream of fast-moving solar wind hit Earth's magnetic field, igniting a ring of auroras around the South Pole. Minoru Yoneto saw the red-purple glow all the way from Queenstown, New Zealand:
"We were lucky to catch another Southern Lights display during my stargazing tour," says Yoneta. "Our guests were excited to photograph them using their own cameras."
Queenstown is at 45 degrees south latitude--a considerable distance from the South Pole. That's why the auroras looked red. Auroras circling the South Pole must reach very high above Earth's surface to be visible half a hemisphere away. At altitudes greater than ~200 km, auroras turn red. The ruby glow occurs when high energy particles from space hit oxygen atoms at the top of the atmosphere. Ionized molecular nitrogen adds a dash of purple to the high-altitude palette.
More red Southern Lights are possible on Nov. 18th or 19th when a new stream of solar wind is expected to arrive. The gaseous material is flowing from a relatively small hole in the sun's atmosphere. Queenstown stargazers, charge your cameras!
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.
An interplanetary shock wave hit Earth's magnetic field on April 19th around 23:50 UT. When the disturbance arrived, the density of solar wind flowing around our planet abruptly quadrupled and a crack opened in Earth's magnetic field. The resulting G2-class geomagnetic storm sparked unusual "electric blue" auroras.
"I've been flying airplanes for 20 years and photographing aurora for 10 years, but I've never seen anything like this before" reports pilot Matt Melnyk, who photographed the display from 39,000 feet. "Electric blue auroras!" he says. "This was while on a red eye flight from Edmonton to Toronto around 4 am over northern Manitoba. Unbelievable sky. I was able to grab some hasty shots with a cell phone."
Auroras are usually green--a sign of oxygen. Rare blue auroras are caused by nitrogen molecules. Energetic particles striking N2+ at the upper limits of Earth's atmosphere can produce an azure glow during intense geomagnetic storms.
What is an interplanetary shock wave? It is a supersonic disturbance in the gaseous material of the solar wind. These waves are usually delivered by coronal mass ejections (CMEs). Indeed, this one might have been a minor CME that left the sun unrecognized earlier this week.
Alternately, it might have been an unusually sharp co-rotating interaction region (CIR). CIRs are transition zones between slow- and fast-moving streams of solar wind. They contain plasma density gradients and magnetic fields that often do a good job sparking auroras.
See also: 'Strong New Moon, Solar Activity and Gateways Ahead' by Sandra Walter, Wayshower, Ascension Guide and Gatekeeper
A strong geomagnetic storm was brewing in the skies above Alberta, Canada, on Sept. 27th when photographer Alan Dyer looked up and saw a ribbon of purple light arcing cross the sky. It was the mysterious aurora known as "Steve":
"The Steve arc appeared for only about 20 minutes, starting at 10:45 pm MDT, during a lull in the main display," says Dyer, who captured the arc in a 6-shot, 360o panorama.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."
"We seem to be ideally located in the Canadian Prairies for sighting Steve, as we often get the main aurora to our north, placing Steve overhead or to our south," notes Dyer.
No one fully understands the underlying physics of the purple ribbon. One of the European Space Agency's Swarm satellites flew straight through Steve during a previous apparition. Data revealed a relatively hot river of gas, about 25 km wide, flowing rapidly through Earth's outer atmosphere. "Steve seems to be a thermal emission from hot flowing gas rather than from precipitating electrons," says Dyer, "but his origin and nature are still mysterious." 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
In the Lofoten Islands of Norway, Spaceweather.com reader Rob Stammes operates a magnetic observatory. Twenty-four hours a day, he measures the strength and direction of the local magnetic field as well as electrical currents running through the ground. During geomagnetic storms, his chart recordings go haywire. On Jan. 13th, something different happened. They rang like a bell:
"For about an hour, electrical currents in the ground beneath my observatory flowed back and forth with a sinusoidal period near 2 minutes," says Stammes. "This is rare."
These are natural ultra-low frequency oscillations known to researchers as "pulsations continuous" (Pc). The physics is familiar to anyone who has studied bells or resonant cavities. Earth's magnetic field carves out a cavity in the surrounding solar wind. Gusts of solar wind can make the cavity "ring" akin to a bell (references: #1, #2, #3). Human ears cannot hear this ringing; it is electromagnetic rather than acoustic. The physical effect is felt beneath our feet. As the cavity vibrates, magnetic fields swing back and forth, causing electrical currents to flow through the ground below.
The Pc waves Stammes detected are a variety known as Pc4, which oscillate in the frequency range 6.7–22 mHz. Such waves are good at energizing particles trapped in Earth's magnetic field and often cause local outbursts of bright auroras. www.spaceweather.com
Similar occurrences were also reported on 12 September and 23 October 2016:
http://www.ascensionnow.co.uk/quick-info/-earths-magnetic-field-rings-like-a-bell - 12 Sept. 2016
http://www.ascensionnow.co.uk/quick-info/sinusoidal-ground-currents-in-norway - 23 Oct. 2016
Six days after Earth entered a stream of high-speed solar wind ... we're still inside. The solar wind continues to blow faster than 500 km/s on Oct. 31st. Although it is not as gusty as it was during first contact on Oct. 25th, the relentless pressure of the sun's electrically charged wind on Earth's magnetic field is causing the poles to glow with beautiful auroras. Marketa S. Murray sends this picture from Fairbanks, Alaska, on Oct. 29th:
"When you stand there and the whole sky is just dancing overhead, your adrenaline and endorphin get so high," says Murray. "It's mind blowing every time it happens. It never gets old, even for an Alaskan!"
Until Earth fully exits this stream, polar auroras remain likely. A good way to follow the action is to tune into a live webcam in Sweden's Abisko National Park. "We have seen the lights nearly every night in October!" says Chad Blakley of Lights over Lapland, who operates the camera.
Watch it now. www.spaceweather.com
Not all space weather occurs high overhead. Sometimes it happens in the soil beneath our feet. Example: On Oct. 23rd in the Lofoten Islands of Norway, electrical currents began to flow through the ground, back and forth with a sinusoidal period of 74 seconds. Rob Stammes recorded the phenomenon at his geomagnetic observatory:
"Just after midnight UTC and around 02.36 local time, my ground current instruments picked up these very stable pulsations," says Stammes.
What's happening here? Ground currents are a sign of changing magnetic fields. Earth's magnetic field around the Lofoten Islands was swinging back and forth, inducing a sinusoidal amperage in the soil beneath Stamme's observatory.
These are natural ultra-low frequency oscillations known to researchers as "pulsations continuous" (Pc). The physics is familiar to anyone who has studied bells or resonant cavities. Earth's magnetic field extends out into space and carves out a cavity in the surrounding solar wind. Pressure fluctuations in the solar wind can excite wave modes in the cavity--usually in a noisy cacophany of many frequencies, but sometimes with almost-monochromatic purity. In such cases, Earth's magnetic field "rings like a bell" with slow tones that reach all the way down to the ground. That's what happened on Oct. 23rd. References: #1, #2, #3.
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.
In the Lofoten Islands of Norway, Spaceweather.com reader Rob Stammes operates a magnetic observatory. 24 hours a day, he measures the strength and direction of the local magnetic field as well electrical currents running through the ground. During geomagnetic storms, his chart recordings go haywire. On Sept. 12th, something different happened. They rang like a bell:
"During the morning and especially around noon, sinusoidal pulsations appeared on my instruments," says Stammes. "The period was close to 115 seconds."
These are natural ultra-low frequency oscillations known to researchers as "pulsations continuous" (Pc). The physics is familiar to anyone who has studied bells or resonant cavities. Earth's magnetic field carves out a cavity in the surrounding solar wind. Pressure fluctuations in the solar wind can excite wave modes in this cavity much like Stammes observed. References: #1, #2, #3.
The Sept. 12th oscillations are Pc4 waves; in other words, their frequencies fall in the range 6.7–22 mHz. Pc4 waves, and their even lower frequency cousins Pc5 waves (1.7–6.7 mHz), can have an energizing influence on particles in Earth's inner magnetosphere because the waves resonate with the natural motion of particles around the geomagnetic field. Perhaps it is no surprise, then, that bright auroras were observed on both Sept. 11th and 12th.
Ole Salomonsen photographed these from the window of an airplane just before sunrise in Norway:
"To get the shot was not easy," says Salomonsen. "I had to use a handheld camera in a moving plane! To create some darkness, I draped one of my jackets to over me and the window to prevent cabin-light reflections ruining the shot. The people sitting next to me probably must have had a good laugh :) Anyway I think it was worth it. Observing the auroras from air is definitely special."
Rob Stammes has been monitoring magnetic pulsations in Norway for years. "They seem to occur most often around the equinoxes," he says. That means we should stay tuned for more. It is aurora season, after all.
For reasons researchers don't fully understand, auroras love equinoxes. At this time of year even a gentle gust of solar wind can spark a bright display. Tomorrow, Sept.23rd, is the northern autumnal equinox. Perfect timing: a CME is expected to deliver a glancing blow to Earth's magnetic field on Sept. 23rd. The impact will probably be weak, but on the first night of autumn, weak may be strong enough. High-latitude sky watchers should be alert for equinox auroras. www.spaceweather.com
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