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GALLERY: Solar blast

A CORONAL MASS EJECTION, or CME, has been spotted erupting away from the Sun, in images taken by the Solar and Heliospheric Observatory (SOHO) spacecraft.

According to the SOHO web site, a CME is a “huge magnetic bubble of plasma that erupts from the Sun’s corona and travels through space at high speed.” Plasma is gas that has been ” heated to sufficiently high temperatures that the atoms ionise”.

When a CME occurs, the plasma shoots out into space and travels through the Solar System. If the timing is right (or wrong, depending on your point of view), a CME can head directly toward Earth.

The first image is a wide field, showing the CME in action on January 14, 2014. The Sun has been blocked out in order to show detail in its outer atmosphere. (The white circle shows the size of the Sun – 1.4 million kilometres, or 870,00 thousand miles, in diameter.) The bright point of light in the top right is the planet Venus. (The white flare on either side of Venus is not real; it is an artifact of the imaging process.)

The second image shows a slightly narrower field, again with the Sun blocked out.

SOHO coronograph image of a CME

A SOHO image of a coronal mass ejection spotted on January 14, 2014. The bright spot in the upper right corner is the planet Venus.

SOHO coronograph image of a CME

Another SOHO view of the January 14, 2014 coronal mass ejection.

SOHO orbits the Sun at a special location between the Sun and the Earth called the L1 Lagrange point. At this location, the gravity of the Sun and Earth balances out, enabling the spacecraft to circle the Sun while always staying on a line between Earth and Sun. It is owned and operated jointly by NASA and the European Space Agency.

Adapted from information issued by NASA and ESA.

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Sun sends an explosion our way

SOHO image of a CME

The Solar Heliospheric Observatory spacecraft captured these images of the sun spitting out a coronal mass ejection on March 15, 2013.

ON MARCH 15, the Sun erupted with an Earth-directed coronal mass ejection (CME), a solar phenomenon that can send billions of tonnes of solar particles into space and can reach Earth one to three days later and affect electronic systems in satellites and on the ground.

Experimental NASA research models, based on observations from the Solar Terrestrial Relations Observatory (STEREO) and ESA/NASA’s Solar and Heliospheric Observatory spacecraft, show that the CME left the Sun at speeds of around 14,50 kilometres per second, which is a fairly fast speed for CMEs. Historically, CMEs at this speed have caused mild to moderate effects when they reach Earth.

The NASA research models also show that the CME may pass by the Spitzer (an Earth-orbiting observatory) and Messenger (Mercury orbiter) spacecraft. NASA has notified their mission operators. There is, however, only minor particle radiation associated with this event, which is what would normally concern operators of interplanetary spacecraft since the particles can trip on-board computer electronics.

Earth-directed CMEs can cause a space weather phenomenon called a geomagnetic storm, which occurs when they connect with the outside of the Earth’s magnetic envelope, the magnetosphere, for an extended period of time.

In the past, geomagnetic storms caused by CMEs such as this one have usually been of mild to medium strength.

In the USA, NOAA’s Space Weather Prediction Center is the United States Government official source for space weather forecasts, alerts, watches and warnings.

In Australia, the solar monitoring and notifications are the responsibility of IPS Radio and Space Services.

Adapted from information issued by NASA / GSFC. Image credit: ESA & NASA / SOHO.

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Video – The Sun unleashes its fury

TO US DOWN HERE ON THE GROUND, the Sun seems unchanging and ever-reliable on a day-to-day basis. But satellites reveal the reality to be very different. Our nearest star is actually a boiling, roiling cauldron of hot gases, unseen magnetic fields and titanic explosions.

Those explosions are called coronal mass ejections, or CMEs, and they shoot enormous clouds of particles far out into the Solar System. Sometimes they hit Earth…but fortunately we’re protected by our planet’s strong magnetic field and thick atmosphere.

The Sun produced about a dozen CMEs between November 22 and 28, 2011. The SOHO spacecraft—which monitors the Sun 24/7—spotted them blasting out in different directions. The following video clip comprises over 1,300 frames, and gives us a sped-up view of those eight eventful days on the Sun:

In order to see the CMEs, SOHO had to block out the glare of the Sun using a coronagraph (black circle). A separate instrument took images of the Sun at the same time (superimposed in the middle) so that we could get the best of both worlds.

The next video was produced from images taken with a different Sun-monitoring spacecraft, the Solar Dynamics Observatory. It shows a portion of an extremely long filament (over 1,000,000 km) that was stretched across much of the face of the Sun and gracefully erupted into space (November 14, 2011).

Filaments are cooler gas structures that are tethered to the Sun by magnetic forces. About the upper third of this filament rose up and broke away, but the other two-thirds still remains in sight. The images were taken in extreme ultraviolet light. The clip covers about 12 hours of activity.

Finally, here’s an amazing video that gives us a complete time-lapse of the Sun spanning the entire months of September, October and November 2011 as seen through the SWAP ultraviolet instrument aboard yet another Sun-monitoring satellite, the European Space Agency’s Proba-2 (PRoject for OnBoard Autonomy).

Adapted from information issued by NASA / SDO / ESA.

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Two massive solar eruptions

THE SUN BLEW OUT TWO sizeable ‘coronal mass ejections’ that headed in just about opposite directions over about a two-day period (July 24-25, 2011). Both of these were from the far side of the Sun and had no impact on Earth.

A coronal mass ejection, or CME, is a huge magnetic bubble of plasma that erupts from the Sun’s corona (the outermost layer of the solar atmosphere) and travels through space at high speed.

In the video—which has been put together from a series of still images and sped up—the Sun (represented real-size by the white circle) and some additional area around it is blocked out with an occulting disc so that the fainter details in the corona can be seen.

To give you an idea of the size of these CMEs, look at the white circle that represents the Sun and remember that the Sun is 109 times wider than the Earth!

The images were taken by the STEREO (Ahead) spacecraft.

Adapted from information issued by NASA.

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Comet’s death dive into the Sun

A TYPE OF COMET KNOWN AS a sun-grazer has met a fiery end, plunging into the Sun and evaporating.

The event was captured by the Solar Dynamics Observatory (SOHO) spacecraft, which continually monitors the Sun. In the video above, the comet can be seen approaching from the bottom right.

According to SOHO Project Scientist Bernhard Fleck, “this is one of the brightest sun-grazers SOHO has recorded…”

Comets diving in towards the Sun are a fairly common event.

Scientists were delighted with this particular event—the SOHO spotted the comet as it disintegrated over about a ten-hour period, something never observed before.

The angle of the comet’s orbit brought it across the front half of the Sun where it seemed to brighten when it stuck hotter masses of particles above the Sun’s surface.

Adapted from information issued by NASA / ESA.

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Spotless Sun

SOHO image of the Sun with no sunspots

Periods of inactivity are normal for the Sun, but the recent period has gone on longer than usual. New computer simulations imply that the long quiet spell resulted from changing flows of hot plasma within the Sun. Image courtesy NASA / SOHO.

  • Sunspots come and go in an 11-year cycle from one minimum to the next
  • Recent minimum period went on for much longer than usual
  • Scientists say the cause is disruptions in the Sun’s ‘plasma rivers’

THE SUN HAS BEEN IN THE NEWS a lot lately because it’s beginning to send out more flares and solar storms. Its recent turmoil is particularly newsworthy because the Sun was very quiet for an unusually long time.

Astronomers had a tough time explaining the extended solar minimum. But new computer simulations imply that the Sun’s long quiet spell resulted from changing flows of hot plasma within it.

“The Sun contains huge rivers of plasma similar to Earth’s ocean currents,” says Andres Munoz-Jaramillo, a visiting research fellow at the Harvard-Smithsonian Centre for Astrophysics (CfA). “Those plasma rivers affect solar activity in ways we’re just beginning to understand.”

The Sun is made of a fourth state of matter—plasma—in which negative electrons and positive ions flow freely. Flowing plasma creates magnetic fields, which lie at the core of solar activity like flares, eruptions, and sunspots.

Astronomers have known for decades that the Sun’s activity rises and falls in a cycle that lasts 11 years on average. At its most active, called solar maximum, dark sunspots dot the Sun’s surface and frequent eruptions send billions of tons of hot plasma into space.

If the plasma hits Earth, it can disrupt communications and electrical grids and short out satellites.

Spotless days

During solar minimum, the Sun calms down and both sunspots and eruptions are rare. The effects on Earth, while less dramatic, are still significant.

For example, Earth’s outer atmosphere shrinks closer to the surface, meaning there is less drag on orbiting space junk.

Also, the solar wind that blows through the solar system (and its associated magnetic field) weakens, allowing more cosmic rays to reach us from interstellar space.

Sunspot cycles over the last century

Sunspot cycles over the last century. The blue curve shows the cyclic variation in the number of sunspots. Red bars show the cumulative number of sunspot-less days. The minimum of sunspot cycle 23 was the longest in the space age, having the largest number of spotless days. Image courtesy Dibyendu Nandi et al.

The most recent solar minimum had an unusually long number of spotless days—780 days during 2008-2010. In a typical solar minimum, the Sun goes spot-free for about 300 days, making the most recent minimum the longest since 1913.

“The last solar minimum had two key characteristics—a long period of no sunspots and a weak polar magnetic field,” explains Munoz-Jaramillo. (A polar magnetic field is the magnetic field at the Sun’s north and south poles.) “We have to explain both factors if we want to understand the solar minimum.”

Plasma rivers

To study the problem, Munoz-Jaramillo used computer simulations to model the Sun’s behaviour over 210 activity cycles spanning some 2,000 years.

He specifically looked at the role of the ‘plasma rivers’ that circulate from the Sun’s equator to higher latitudes. These currents flow much like Earth’s ocean currents: rising at the equator, streaming toward the poles, then sinking and flowing back to the equator.

Cutaway diagram of the Sun showing the Great Conveyor Belt

In this artistic cutaway view of the Sun, the Great Conveyor Belt appears as a set of black loops connecting the stellar surface to the interior. Image courtesy Andrés Muñoz-Jaramillo / Harvard CfA.

At a typical speed of 65 kilometres per hour, it takes about 11 years to make one loop.

Munoz-Jaramillo and his colleagues discovered that the Sun’s plasma rivers speed up and slow down like a malfunctioning conveyor belt. They find that a faster flow during the first half of the solar cycle, followed by a slower flow in the second half of the cycle, can lead to an extended solar minimum.

The cause of the speed-up and slowdown likely involves a complicated feedback between the plasma flow and solar magnetic fields.

“It’s like a production line—a slowdown puts ‘distance’ between the end of the last solar cycle and the start of the new one,” says Munoz-Jaramillo.

The ultimate goal of studies like this is to predict upcoming solar maxima and minima…both their strength and timing. The team focused on simulating solar minima, and say that they can’t forecast the next solar minimum (which is expected to occur in 2019) just yet.

“We can’t predict how the flow of these plasma rivers will change,” explains lead author Dibyendu Nandy (Indian Institute of Science Education and Research, Kolkata). “Instead, once we see how the flow is changing, we can predict the consequences.”

Adapted from information issued by the Harvard-Smithsonian Centre for Astrophysics.

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Amazing eclipse image

Composite image of the July 11, 2010, total solar eclipse.

Three different images, taken by different instruments, have been combined to produce this composite image of the July 11, 2010, total solar eclipse.

This incredible record of July 11’s total solar eclipse is actually three images in one, each taken by different instruments to bring out detail in different parts of the Sun.

The outer, redder part of the image shows the Sun’s outer corona, or outer atmosphere, as seen by the Large Angle Spectrometric Coronagraph (LASCO) on the SOHO spacecraft and shown in red false colour. SOHO has been studying the Sun for years from its vantage point between the Earth and the Sun.

LASCO uses a disc to blot out the bright sun and the inner corona so that the faint outer corona can be monitored and studied.

The inner black-and-white part shows the Sun’s inner corona, and is an image taken from Easter Island by the Williams College Expedition.

Finally, at the very centre is ultraviolet image of the Sun’s surface, taken by the Atmospheric Imaging Assembly on Solar Dynamics Observatory (SDO), a recently-launched Sun-monitoring spacecraft.

Image credits: Williams College Eclipse Expedition — Jay M. Pasachoff, Muzhou Lu, and Craig Malamut; SOHO’s LASCO image courtesy of NASA/ESA; solar disk image from NASA’s SDO; compositing by Steele Hill, NASA’s Goddard Space Flight Centre.

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Sun’s size surprises scientists

The Sun’s disc

The Sun’s disc showing active region 10486, which became the largest sunspot seen by the SOHO satellite.

  • Sun’s size normally varies
  • But has stayed the same for 12 years

Astronomers have found that in recent times the Sun’s size has been remarkably constant. Normally its diameter varies slightly, but the scientists have found that it has changed by less than one part in a million over the last 12 years.

“This constancy is baffling, given the violence of the changes we see every day on the Sun’s surface and the fluctuations that take place over an 11-year solar cycle,” said Dr Jeff Kuhn, associate director of the University of Hawaii Institute for Astronomy (IfA) who is responsible for Haleakala Observatories.

Kuhn’s work is part of worldwide efforts to understand the influence of the Sun on Earth’s climate. “We can’t predict the climate on Earth until we understand these changes on the Sun,” he said.

Kuhn and his colleagues used NASA’s long-lived Solar and Heliospheric Observatory (SOHO) satellite to monitor the Sun’s diameter, and they will soon repeat the experiment with much greater accuracy using NASA’s new Solar Dynamics Observatory (SDO), which was launched on February 11.

According to Kuhn, the ultimate solution to this puzzle will depend on probing the smallest observable scales of the solar surface using the Advanced Technology Solar Telescope (ATST), which is scheduled for completion on Haleakala in 2017.

“To be able to predict what the Sun will do, we need both the big picture and the details,” said Kuhn. “Just as powerful hurricanes on Earth start as a gentle breeze, the analogues of terrestrial storms on the Sun start as small kinks in the Sun’s magnetic field.”

Adapted from information issued by the University of Hawaii at Manoa’s Institute for Astronomy / SOHO / MDI consortium.