Time to grab your silver surfboards because scientists utilizing the Atmospheric Imaging Assembly (AIA) instrument on-board NASA’s Solar Dynamics Observatory (SDO), have picked up on quasi-periodic waves in the low solar corona that travel at speeds as high as 2,000 kilometers per second (4.5 million miles per hour). Just think… We could ride that tasty wave to the Moon and back about 16 times during lunch break and still have time for coffee!
Presenting the findings today at the annual meeting of the Solar Physics Division of the American Astronomical Society is Dr. Wei Liu, a Stanford University Research Associate at the Lockheed Martin Solar and Astrophysics Laboratory (LMSAL) at the company’s Advanced Technology Center (ATC) in Palo Alto. His research has provided concrete evidence of propagating fast mode magnetosonic waves at such high speeds in the Sun’s low atmosphere. We’ve known for awhile that hot plasma will produce a “ripple effect” – much like a bubble popping to the surface when heating gravy. While computer simulations, models and theories speculated how it occurred, it wasn’t until now that these waves have been directly observed. Why? Because we simply weren’t quick enough.
“It is the high temporal and spatial resolution of AIA that enables us to see these waves clearly for the first time. AIA takes high sensitivity, extreme ultraviolet (EUV) pictures of the solar corona at spatial scales down to 1,100 kilometers, every 12 seconds with 0.1-2 second exposures,” said Dr. Liu, who led the analysis of the waves. “In addition, AIA’s full Sun field of view at seven simultaneous wavelengths allows us to track them over large spatial and temperature ranges.”
Just check this bad boy out…
Lasting anywhere from 30 to 200 seconds, the hot arches center around flare nuggets and follow the wake of coronal mass ejection areas… traveling along the magnetic loops. “Their characteristic spatial and temporal scales and dispersion relation agree with theoretical expectations of fast mode magnetosonic waves, and are reproduced in our high fidelity 3D computer simulations,” said Prof. Leon Ofman of the Catholic University of America, part of the team that made the discovery. “They seem to be a common phenomenon. During the first year of the SDO mission, despite the Sun being relatively quiet, we have seen about a dozen such waves,” said Dr. Karel Schrijver, principal physicist of LMSAL. “Although their exact trigger mechanism is currently under investigation, they appear to be intimately related to flares that sometimes exhibit pulsations at similar frequencies.”
These types of waves are quite probably responsible for elemental – yet still mysterious – processes on the solar surface, such as heating the corona to millions of degrees, accelerating the solar wind, triggering remote eruptions, and delivering energy and information between different parts of the atmosphere. Through direct observance, we’re able to begin to unravel the physics and advance our knowledge of the Sun-Earth connection.
“This discovery and analysis is very significant because we are witnessing phenomena of which we were previously unaware. In light of this discovery, the more we look at solar flares, the more of these waves we see, and as observation and analysis lead to insight, the better we will understand the processes involved,” said Dr. Alan Title, AIA Principal Investigator at LMSAL who first noticed the fast propagating waves in routine AIA movies. “The findings announced today are an example of the fruit of a two decade long collaboration, of which we are enormously proud, between Lockheed Martin and Stanford University.”
Our Sun on June 6, 2011. Credit: Credit: Cesar Cantu from the Chilidog Observatory in Monterrey, Mexico.
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Are we headed into the 21st century version of the Maunder Minimum? Three researchers studying three different aspects of the Sun have all come up with the same conclusion: the Sun’s regular solar cycles could be shutting down or going into hibernation. A major decrease in solar activity is predicted to occur for the next solar cycle (cycle #25), and our current solar cycle (#24) could be the last typical one. “Three very different types of observations all pointing in the same direction is very compelling,” said Dr. Frank Hill from the National Solar Observatory, speaking at a press briefing today. “Cycle 24 may be the last normal one, and 25 may not even happen.”
Even though the Sun has been active recently as it heads towards solar maximum in 2013, there are three lines of evidence pointing to a solar cycle that may be going on hiatus. They are: a missing jet stream, slower activity near the poles of the sun and a weakening magnetic field, meaning fading sunspots. Hill, along with Dr. Richard Altrock from the Air Force Research Laboratory and Dr. Matt Penn from the National Solar Observatory independently studied the different aspects of the solar interior, the visible surface, and the corona and all concur that cycle 25, will be greatly reduced or may not happen at all.
Solar activity, including sunspot numbers, rises and falls on average about every 11 years – sometimes the cycles are as short as 9 years, other times it is as long as 13 years. The Sun’s magnetic poles reverse about every 22 years, so 11 years is half of that magnetic interval cycle.
"Butterfly diagram" shows the position of sunspots over 12 solar cycles. Sunspots emerge over a range of latitudes centered on migratory jet streams that follow a clear pattern, trending from higher latitudes to lower latitudes on the Sun. The active latitudes are associated with mobile zonal flows or "jet streams" that vary through the cycle. Credit: SWRI
The first line of evidence is a slowing of a plasma flow inside the Sun, an east/west flow of gases under the surface of the Sun detected via seismology with spacecraft like the Solar Dynamics Observatory (SDO)or SOHO and also with the Global Oscillation Network Group (GONG) observing stations, a system that measures pulsations on the solar surface to understand the internal structure of the sun. The flow of plasma normally indicates the onset of sunspot formation for the next solar cycle. While this river ebbs and flows during the cycle, the “torsional oscillations,” — which starts at mid-latitudes and migrates towards the equator — and normally begins forming for the next solar cycle has not yet been detected.
Latitude-time plots of jet streams under the Sun's surface show the surprising shutdown of the solar cycle mechanism. New jet streams typically form at about 50 degrees latitude (as in 1999 on this plot) and are associated with the following solar cycle 11 years later. New jet streams associated with a future 2018-2020 solar maximum were expected to form by 2008 but are not present even now, indicating a delayed or missing Cycle 25. Credit: SWRI
Hill said the above graphic is key for understanding the issue. “The flow for Cycle 25 should have appeared in 2008 or 2009 but it has not and we see no sign of it,” he said. “This indicates that the start of Cycle 25 may be delayed to 2021 or 2022, with a minimum great that what we just experienced, or may not happen at all.”
Plots of coronal brightness against solar latitude show a "rush to the poles" that reflects the formation of subsurface shear in the solar polar regions. The current "rush to the poles" is delayed and weak, reflecting the lack of new shear under the photosphere. Note the graph depicts both north and south hemispheres overlaid into one map of solar magnetic activity, and that the patterns correspond with the butterfly diagram above. Credit: SWRI
The second line of evidence is slowing of the “rush to the poles,” the rapid poleward march of magnetic activity observed in the Sun’s faint corona. Altrock said the activity in the solar corona follows same oscillation pattern described by Hill, and that they have been observing the pattern for about 40 years. The researchers now see a very weak and slow pattern in this movement.
“A key thing to understand is that those wonderful, delicate coronal features are actually powerful, robust magnetic structures rooted in the interior of the Sun,” Altrock said. “Changes we see in the corona reflect changes deep inside the Sun.”
In a well-known pattern, new solar activity emerges first at about 70 degrees latitude at the start of a cycle, then towards the equator as the cycle ages. At the same time, the new magnetic fields push remnants of the older cycle as far as 85 degrees poleward. “In previous solar cycles, solar maximum occurred when the rush to the poles reached an average latitude of 76 degrees,” Altrock said. “Cycle 24 started out late and slow and may not be strong enough to create a rush to the poles, indicating we’ll see a very weak solar maximum in 2013, if at all. It is not clear whether solar max as we know it.”
Altrock added that if the “rush” doesn’t occur, no one knows what will happen in the future because no one has modeled what takes place without this rush to the poles.
Average magnetic field strength in sunspot umbras has been steadily declining for over a decade. The trend includes sunspots from Cycles 22, 23, and (the current cycle) 24. Credit: SWRI
The third line of evidence is a long-term weakening trend in the strength of sunspots. Penn, along with his colleague William Livingston predict that by Cycle 25, magnetic fields erupting on the Sun will be so weak that few if any sunspots will be formed.
Using more than 13 years of sunspot data collected at the McMath-Pierce Telescope at Kitt Peak in Arizona, Penn and Livingston observed that the average field strength declined about 50 gauss per year during Cycle 23 and now in Cycle 24. They also observed that spot temperatures have risen exactly as expected for such changes in the magnetic field. If the trend continues, the field strength will drop below the 1,500 gauss threshold and spots will largely disappear as the magnetic field is no longer strong enough to overcome convective forces on the solar surface.
“Things are erupting on the sun,” Penn said, “but they don’t have the energy to create sunspots.”
But back in 1645-1715 was the period known as the Maunder Minimum, a 70-year period with virtually no sunspots. The Maunder Minimum coincided with the middle – and coldest part – of the Little Ice Age, during which Europe and North America experienced bitterly cold winters. It has not been proven whether there is a causal connection between low sunspot activity and cold winters. However lower earth temperatures have been observed during low sunspot activity. If the researchers are correct in their predictions, will we experience a similar downturn in temperatures?
Hill said that some researchers say that the Sun’s activity can also play a role in climate change, but in his opinion, the evidence is not clear-cut. Altrock commented he doesn’t want to stick his neck out about how the Sun’s declining activity could affect Earth’s climate, and Penn added that Cycle 25 may provide a good opportunity to find out if the activity on the Sun contributes to climate change on Earth.
Lead image thanks to César Cantú in Monterrey, Mexico at the Chilidog Observatory. See more at his website, Astronomía Y Astrofotografía.
You can follow Universe Today senior editor Nancy Atkinson on Twitter: @Nancy_A. Follow Universe Today for the latest space and astronomy news on Twitter @universetoday and on Facebook.
The solar minimum occurs approximately every 11 years when fewer sunspots like these appear. Image credit: NASA/Goddard Space Flight Center
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Since Galileo’s time, humans have been going essentially blind following sunspots. But, as our technology advanced, our blindness as to solar causes and effects was lifted. Thanks to Edward Maunder’s work in the late 1800s, we began to “see” a bit better as the 11-year sunspot cycle emerged. From earlier observation, the “Maunder Minimum” – a period roughly spanning 1645 to 1715 when sunspots were a rarity – was established and the hypothesis of the Little Ice Age came forward. But no proof exists that solar minimum affects much here on Earth… Or does it?
Modern technology has allowed us to study solar phenomena in ways our predecessors would never have imagined. In 2008, scientists were able to document the solar minimum as one of the most prolonged and weak since the advent of space-based instrumentation. But with our terrestrial blinders off, it didn’t take long to establish the lack of solar activity didn’t correspond with solar magnetism. Quite simply put, auroral activity didn’t decrease proportionately… until 8 months later. A paper in Annales Geophysicae that appeared on May 16, 2011 reports these effects on Earth did in fact reach a minimum – the lowest levels of the century. Solar wind speed along with the strength and direction of the magnetic field seems to have taken a dominant role.
“Historically, the solar minimum is defined by sunspot number,” says space weather scientist Bruce Tsurutani at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., who is first author on the paper. “Based on that, 2008 was identified as the period of solar minimum. But the geomagnetic effects on Earth reached their minimum quite some time later, in 2009. So we decided to look at what caused the geomagnetic minimum.”
Geomagnetic effects are based on the Sun’s power to alter Earth’s magnetic fields. Measured with a magnetometer, these effects usually produce nothing more than auroral activity. But extreme examples could include power grid failures, satellite disruption and more. Understanding our space weather is important and three factors come to bear: the speed of the solar wind, the strength of the interplanetary magnetic field and which direction it is flowing. The team – which also included Walter Gonzalez and Ezequiel Echer of the Brazilian National Institute for Space Research in São José dos Campos, Brazil – examined each of these factors in sequence.
At the onset, the researchers agreed the interplanetary magnetic field was at a low in 2008 and 2009. This was obviously a factor to the geomagnetic minimum, but since effects didn’t decrease in 2008, it couldn’t be the sole reason. To study solar wind speed, the employed NASA’s Advanced Composition Explorer (ACE) and data revealed the speed of the solar wind stayed high during the sunspot minimum. It took a period of time to decay – one that matched the decline in geomagnetic effects. The next step was to determine the cause – and the smoking gun appeared to be coronal holes. Here is where solar wind can burst forth from the center at speeds of 500 miles per second, but slows down when coming from the sides and extends across space.
“Usually, at solar minimum, the coronal holes are at the sun’s poles,” says Giuliana de Toma, a solar scientist at the National Center for Atmospheric Research whose research on this topic helped provide insight for this paper. “Therefore, Earth receives wind from only the edges of these holes, and it’s not very fast. But in 2007 and 2008, the coronal holes were not confined to the poles as normal.”
Coincidental evidence? Not hardly. In 2008 the coronal holes remained at low solar latitudes with their winds pointed directly toward Earth. Not until 2009 did they move toward the Sun’s poles and geomagnetic effects and sightings of the aurora went proportionally along with it. It’s even been theorized coronal holes may be responsible for minimizing the southward direction of the interplanetary magnetic field as well. Such a combination of all factors are setting the stage for geomagnetic minimum, but study is still needed to help understand and predict such phenomena. To do so well, Tsurutani points out, requires focusing on the tight connection between such effects and the complex physics of the sun. “It’s important to understand all of these features better,” he says. “To understand what causes low interplanetary magnetic fields and what causes coronal holes in general. This is all part of the solar cycle. And all part of what causes effects on Earth.”
First complete image of the far side of the sun taken on June 1, 2011. Click image for larger version. Credit: NASA/STEREO.
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Far out! This is the first complete image of the solar far side, the half of the sun invisible from Earth. Captured on June 1, 2011, the composite image was assembled from NASA’s two Solar TErrestrial RElations Observatory (STEREO) spacecraft. STEREO-Ahead’s data is shown on the left half of image and STEREO-Behind’s data on the right.
You may recall that the two STEREO spacecraft reached opposition (180 degree separation) on February 6 of this year and the science team released a “complete” 360 degree view of the Sun. However, a small part of the sun was inaccessible to their combined view until June 1. This image represents the first day when the entire far side could be seen.
The image is aligned so that solar north is directly up. The seam between the two images is inclined because the plane of Earth’s – and STEREO’s – orbit, known as the “ecliptic”, is inclined with respect to the sun’s axis of rotation. The data was collected by STEREO’s Extreme Ultraviolet Imagers in the SECCHI instrument suites.
The video below explains why seeing the entire Sun is helpful to scientists:
Surfer waves -- initiated in the sun, as they are in the water, by a process called a Kelvin-Helmholtz instability -- have been found in the sun's atmosphere. Credit: NASA/SDO/Astrophysical Journal Letters
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Surf’s up on the Sun! Our favorite gnarly spacecraft, the Solar Dynamics Observatory (SDO) has caught conclusive evidence of classic “surfer waves” in the Sun’s atmosphere. But these waves trump ‘Hawaii Five-O’ surfing big time, as they are about the same size as the continental U.S. Spotting these waves will help our understanding of how energy moves through the solar atmosphere, known as the corona and maybe even help solar physicists be able to predict events like Coronal Mass Ejections.
Just like a surfing wave on Earth, the solar counterpart is formed by the same fluid mechanics — in this case it is a phenomenon known as a Kelvin-Helmholtz instability. Since scientists know how these kinds of waves disperse energy in water, they can use this information to better understand the corona. This in turn, may help solve an enduring mystery of why the corona is thousands of times hotter than originally expected.
“One of the biggest questions about the solar corona is the heating mechanism,” says solar physicist Leon Ofman of NASA’s Goddard Space Flight Center, Greenbelt, Md. and Catholic University, Washington. “The corona is a thousand times hotter than the sun’s visible surface, but what heats it up is not well-understood. People have suggested that waves like this might cause turbulence which cause heating, but now we have direct evidence of Kelvin-Helmholtz waves.”
Even though these waves occur frequently in nature here on Earth, no one had seen them on the Sun. But that was before SDO.
Ofman and colleagues spotted these waves in images taken on April 8, 2010 in some of the first images caught on camera by SDO, which launched in Feburary last year and began capturing data on March 24, 2010. Ofman & team have just published a paper in Astrophysical Journal Letters.
Kelvin-Helmholtz instabilities occur when two fluids of different densities or speeds flow by each other. In the case of ocean waves, that’s the dense water and the lighter air. As they flow past each other, slight ripples can be quickly amplified into the giant waves loved by surfers. In the case of the solar atmosphere, which is made of a very hot and electrically charged gas called plasma, the two flows come from an expanse of plasma erupting off the sun’s surface as it passes by plasma that is not erupting. The difference in flow speeds and densities across this boundary sparks the instability that builds into the waves.
On the sun, the two fluids are both plasmas — expanses of super hot, charged gases — which interact. One is erupting from the surface and shooting past a second plasma that is not erupting. The resulting turbulence is a Kelvin-Helmholtz wave form.
The erupting plasma is likely from a Coronal Mass Ejection, such as was seen earlier this week, where the Sun violently propels massive amounts of high-speed plasma particles into space. So, knowing more about the how the corona is heated and what the conditions are just before the KH waves form might give scientists the ability to predict a the next CME, which is a long-standing goal of solar scientists.
But figuring out the exact mechanism for heating the corona will likely keep solar physicists busy for quite some time. However, SDO’s ability to capture images of the entire sun every 12 seconds with such precise detail will certainly provide the data needed.
You can follow Universe Today senior editor Nancy Atkinson on Twitter: @Nancy_A. Follow Universe Today for the latest space and astronomy news on Twitter @universetoday and on Facebook.
Massive coronal mass ejection on. This image shows the size of the Earth to scale. NASA / SDO / J. Major.
Here’s more video from the huge explosion on the Sun on June 7, 2011, which began at about 06:41 UTC. Not only was this event one of the most spectacular ever recorded, but also one of the best observed, with complementary data from several spacecraft and different vantage points. This video shows data from three different space observatories. The Solar Dynamics Observatory’s Atmospheric Imaging Assembly recorded the amazing event in stunning detail in different wavelengths. Additionally, the Solar & Heliospheric Observatory’s (SOHO) LASCO coronagraph and STEREO’s (Solar Terrestrial Relations Observatory) SECCHI instrument suite observed the prominence and associated CME as they traveled out into the heliosphere. Using LASCO and SECCHI data, the speed of the leading edge of the CME was estimated to be in the range 1200 – 1600 km/s. Model calculations predict that Earth will receive a glancing blow of the CME on June 10, possibly sparking some nice aurorae at high latitudes, according to the SDO team.
The citizen science project Solar Storm Watch predicts a solar storm to reach Earth at 08:00 UTC on June 10, 2011 with a glancing blow 35 degrees behind Earth, with a second storm expected at 19:00 UTC on June 10, 2011, with another glancing blow 32 degrees behind Earth.
The event originated from the almost spotless active region 11226 and was associated with a moderate M2-class X-ray flare. The CME and associated shock wave produced and S1-class radiation storm, which shows up as speckles in the LASCO movies.
The size of the prominence is thought to be at least 75 times the size of Earth. Our Jason Major created a graphic showing the size comparison. Earth is the little teeny tiny blue circle in the top left corner:
A huge and spectacular prominence eruption on the Sun, June 7, 2011. Credit: NASA/Solar Dynamics Observatory
Early this morning (June 7, 2011) an amazingly massive and spectacular event took place on the Sun; a huge prominence eruption, marked by a solar flare and release of energetic particles. Daniel Pendick from the Geeked on Goddard blog described it as a “fountain of plasma that blasts out of the solar surface, spreads outward, and collapses to splat back down.”
“I’ve never seen material released like this before, such a huge amount that falls back down in such a spectacular way,” says Dr. C. Alex Young in the video. “It looks like someone just kicked a giant clod of dirt into the air and it fell back down.” Young added that this event will probably not cause any problems as far as space weather affecting Earth.
Below are some still images of the event from the Solar Dynamics Observatory and (just added at 1755 UTC) a video from SDO showing the event in several different wavelengths.
These images were posted by the Camilla_SDO Twitpic feed.
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This is the peak of the M2.5 class solar flare, which propelled the plasma into space today. Credit: NASA/ Solar Dynamics Observatory, via CamillaSDO on Twitter.
The SDO science teams says: “The Sun unleashed an M-2 (medium-sized) solar flare with a substantial coronal mass ejection (CME) on June 7 that is visually spectacular. The large cloud of particles mushroomed up and fell back down looking as if it covered an area of almost half the solar surface.”
“SDO observed the flare’s peak at 1:41 AM EST. SDO recorded these images in extreme ultraviolet light and they show a very large explosion of cool gas. It is somewhat unique because at many places in the eruption there seems to be even cooler material — at temperatures less than 80,000K.”
Update: The US National Weather Service Space Weather Prediction center has now warned that the solar flare, one of the largest to occur since December 2006, will likely lead to gemagnetic storm activity tomorrow, Wednesday.
The NWS stated: “A dramatic eruption from an otherwise unimpressive NOAA Region 1226 earlier today is expected to cause G1 (minor) to G2 (moderate) levels of geomagnetic storm activity tomorrow, June 8, beginning around 1800 UTC with the passage of a fast CME. A prompt Solar Radiation Storm reached the S1 (minor) level soon after the impulsive R1 (minor) Radio Blackout at 0641 UTC. The Solar Radiation Storm includes a significant contribution of high energy (>100 MeV) protons, the first such occurrence of an event of that type since December 2006.”
You can find updates from the Space Weather Prediction Center at this link.
Here’s the reason for those auroras Tammy was talking about…The Solar Dynamics Observatory captures a beautiful filament eruption from the Sun in the early hours of May 17, 2011 which sent a cloud of plasma into space. This Coronal Mass Ejection was not aimed at Earth but it will likely interact with Earth’s magnetic field by the 19th, so be on the lookout for auroras. The second part of the video is from today, May 18, 2011 and shows some dancing plasma and more “plasma rain” similar to what we showed a last week. few days ago. The Sun’s gravity grabs and pulls the plasma back, even when it appears ready to travel off into space.
The SOHO spacecraft coronagraph captured a sun-diving comet on May 10th and 11th that met its demise as it plunged into the Sun just as Old Sol released a huge flare. The two events were coincidental and not related, but spectacular to see.
The Solar Dynamics Observatory captured some plasma streaming off the Sun, doing a quick dance, and diving back into the surface. This video zooms into an active region over two days (Apr. 30 – May 2, 2011). The cloud of ionized gas, or plasma that comes off the Sun is caused by an active, erupting sunspot. Why does the plasma return instead of streaming off into space? Magnetic forces are pulling the material along magnetic field lines on the Sun, and the plasma follows the Sun’s magnetic fields as it flies outwards, and either returns to the Sun or goes out into space. Here, the plasma returned. What you are seeing is ionized Helium at about 60,000 degrees C. in extreme ultraviolet light.
