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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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Making sense of the solar cycle

THE NUMBER OF SUNSPOTS increases and decreases over time in a regular, approximately 11-year cycle, called the sunspot cycle. The exact length of the cycle can vary. It has been as short as eight years and as long as fourteen, but the number of sunspots always increases over time, and then returns to low again.

Sunspots look dark only because they’re a bit cooler than the surrounding solar surface. In reality, sunspots are still intensely hot—around 3,000 to 4,000 degrees Celsius.

More sunspots mean increased solar activity, when great blooms of radiation known as solar flares or bursts of solar material known as coronal mass ejections (CMEs) shoot off the Sun’s surface.

The highest number of sunspots in any given cycle is designated “solar maximum,” while the lowest number is designated “solar minimum.”

A sunspot group

Sunspot numbers climb and fall over an 11-year cycle.

Each cycle, varies dramatically in intensity, with some solar maxima being so low as to be almost indistinguishable from the preceding minimum.

The last solar maximum was in the year 2000, and the next is expected to occur in early 2013.

Solar cauldron

Sunspots are a magnetic phenomenon. The entire Sun is magnetised with a north and a south magnetic pole just like a bar magnet. The comparison to a simple bar magnet ends there, however, as the Sun’s interior is constantly on the move.

By tracking pressure waves that course through the centre of the Sun, an area of research known as helioseismology, scientists can gain an understanding of what’s deep inside the Sun.

They have found that the magnetic material inside the Sun is constantly stretching, twisting, and crossing as it bubbles up to the surface.

The exact pattern of movements is not conclusively mapped out, but over time they eventually lead to the poles reversing completely.

The Sun flips out

The sunspot cycle happens because the magnetic poles flip—north becomes south and south becomes north—approximately every 11 years. Some 11 years later, the poles reverse again back to where they started, making the full solar cycle actually a 22-year phenomenon.

The Sun behaves similarly over the course of each 11-year cycle no matter which pole is on top, however, so the shorter cycle tends to receive more attention.

Adapted from information issued by NASA / Goddard Space Flight Centre. Images courtesy NSO and SOHO (ESA & NASA).

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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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Solar explosions held by magnetic “ropes”

A coronal mass ejection on the Sun.

Coronal mass ejections (CMEs) are huge explosions on the surface of the Sun that should billions of tonnes of matter into space.

Over the last century, astronomers have become very aware of how just dynamic the Sun really is. One of the most dramatic manifestations of this is a coronal mass ejection (CME) where billions of tons of matter are thrown into space.

If a CME reaches the Earth it creates inclement ‘space weather’ that can disrupt communications, power grids and the delicate systems on orbiting satellites. This potential damage means there is a keen interest in understanding exactly what triggers a CME outburst.

Now a team of researchers from University College London (UCL) have used data from the Japanese Hinode spacecraft, revealing new details of the formation of an immense magnetic structure that erupted to produce a CME on the December 7, 2007.

An eruption on the Sun known as a coronal mass ejection.

NASA's STEREO space probe saw an eruption on the Sun known as a coronal mass ejection.

Lead researcher Dr Lucie Green will present the team’s results on Monday, April 12, at the Royal Astronomical Society (RAS) National Astronomy Meeting in Glasgow.

The Sun’s behaviour is shaped by the presence of magnetic fields that thread through the solar atmosphere. The magnetic fields may take on different shapes from uniform arches to coherent bundles of field lines known as ‘flux ropes’.

Understanding the exact structure of magnetic fields is a crucial part of the effort to determine how the fields evolve and the role they play in solar eruptions.

In particular, flux ropes are thought to play a vital role in the CME process, having been frequently detected in interplanetary space as CMEs reach the vicinity of the Earth.

The formation of the flux rope requires that significant energy is stored in the solar atmosphere. The rope is expected to remain stable whilst the solar magnetic field in the vicinity holds it down.

But at some point the structure becomes unstable and it erupts to produce a CME. Using data from the Hinode spacecraft Dr Green has shown that a flux rope formed in the solar atmosphere over the 2.5 days that preceded the December 2007 event. Evidence for the flux rope takes the form of S shaped structures which are clearly seen by one of the Hinode instruments, the Extreme-Ultraviolet Imaging Telescope.

The key point to understanding and predicting the formation of CMEs is to know when the flux rope becomes unstable. Combining the observations of the S shaped structure with information on how the magnetic field in the region evolves has enabled Dr Green to work out when this happened.

The work shows that over 30% of the magnetic field of the region had been transformed into the flux rope before it became unstable, three times what has been suggested in theory.

Adapted from information issued by RAS. Images courtesy the STEREO Science Centre / NASA / SOHO.