Solar dynamic loops reveal a simultaneous explosion and implosion, plus evidence for magnetic reconnection
Jul 02, 2013
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Solar dynamic loops reveal a simultaneous explosion and implosion, plus evidence for magnetic reconnection
July 2nd, 2013 in Space & Earth / Space Exploration
Image from NASA’s Solar Dynamic Observatory (SDO) at 17.7 nanometres showing the flaring active region on 9 March 2012. The coronal loops that contract during the flare are indicated by the labels L1 to L4, outer to inner. Credit: NASA/SDO/University of Glasgow.
(Phys.org) —Movies of giant loops projecting from the surface of the Sun are giving new insights into the complex mechanisms that drive solar flares and Coronal Mass Ejections (CMEs). These eruptions release vast energy and electrically charged particles that can affect the Earth through space weather. Imagery from NASA's Solar Dynamics Observatory (SDO), used in two separate studies, shows the dynamics of loops before, during and after eruptions. Results have been presented at the National Astronomy Meeting in St Andrews.
Coronal loops are giant magnetic arches filled with hot plasma at temperatures of over a million degrees Celsius. The structures are anchored in the dense photosphere, the visible surface of the Sun. The loops form the building blocks of the corona, the halo surrounding the Sun that can be seen during a total eclipse. They are dynamic structures that oscillate back and forth after explosive events such as solar flares.
Researchers from the University of Glasgow observed four groups of loops that contracted rapidly during a flare on 9 March 2012. The loops had a 'staggered start' to their collapse, showing delays of 60–80 seconds from the inner to the outer loops.
"This event is a great example of a simultaneous implosion and explosion," said Dr Paulo Simões. "Our interpretation is that energy is transferred from the magnetic field to power the flare, leaving a pocket of reduced magnetic support that causes an implosion. The staggering between the loop contractions is caused by the time delay needed for the 'information' about the loss of support to travel outwards."
The loop contractions are triggered at the same time as the flare begins emitting intense X-rays and microwaves. The three outer loops show clear oscillations even as they contract, with distinct periods and phases. After being compressed by the collapsing loops, the flaring loops oscillate until they find a new equilibrium, as indicated by the X-ray emission from the hot plasma. During the contraction a wave blast revealed by extreme ultraviolet radiation spreads away from the source of the flare.
"This presents an intriguing picture of how magnetic energy is moved rapidly around the solar corona during a flare," said Dr Simões.
Flares and CMEs are thought to be driven by a process called magnetic reconnection, in which magnetic field lines in plasma break and then re-join to field lines flowing in the opposite direction. Energy that has built up over days or months is released in just a few minutes.
In a separate study, a team from the University of Warwick has observed the first evidence that loop oscillations are driven directly by magnetic reconnection processes.
"The structure and dynamics of the solar corona can be imaged in exquisite detail and over an unprecedented range of temperatures by SDO. Oscillating loops are a useful tool for probing conditions in the corona. This offers a unique opportunity to discover the tell-tale signatures of magnetic reconnection," said Rebecca White, who presented the findings on Tuesday 2nd July.
The Warwick team used SDO data to study the behaviour of loops following two eruptions: a CME on 3 November 2010 and a solar flare on 8 May 2012. With the first eruption, they saw a coronal loop form below the bubble of material ejected during the CME. There appeared to be a strand connecting the CME with the top of the loop. Unusually, parts of the loop were observed to oscillate in different directions about a central pivot point.
"The loop appears to twist about a fixed point along its length. Not only is the form of this oscillation highly unusual but the coronal loop has a temperature of between 9 and 11 million degrees - this is much hotter than most loops we see, which are generally between 1 and 3 million degrees. This extreme heat has been generated by the reconnection processes," said White. "For the first time we can see a direct link between the reconnection process itself, causing the formation of the loop below the ejected bubble, and the oscillations of the loops."
The second observation showed two separate but adjacent loops oscillating in opposite directions to one another. Previous observations have shown loop oscillations caused by blast waves emanating from the flare, however this pushes the loops in a single direction.
"Again, this cannot be explained by a blast wave since this would push both loops in the same direction. We think that the oscillations here are a direct result of the flare reconnection process changing the structure of the corona between the loops and sucking them towards each. These observations demonstrate that loop oscillations are a valuable tool for studying 3D reconnection processes at work," said White.
More information: R.S. White, E. Verwichte & C. Foullon, First observation of a transverse vertical oscillation during the formation of a hot post flare loop, A&A, 545, A129 (2012)
Provided by Royal Astronomical Society
"Solar dynamic loops reveal a simultaneous explosion and implosion, plus evidence for magnetic reconnection." July 2nd, 2013.
Jun 26, 2013 08:20 PM EDT
NASA's Biggest Day: IRIS Blastoff in 24-Hours to Study the Massive Coronal Hole on the Sun
IRIS
Space engineers at Vandenberg Air Force Base in California couple the Pegasus XL rocket with the Interface Region Imaging Spectrograph, or IRIS, solar observatory to the Orbital Sciences L-1011 carrier aircraft.
NASA will launch its IRIS mission on Thursday, June 27 at 10:27 p.m. EDT. Live NASA Television launch coverage begins at 9 p.m.
On June 18, 2013, NASA had discovered a giant hole in the Sun, which is heading our way.
NASA's Solar Dynamics Observatory had captured a picture of the sun, showing a huge coronal hole, which spread out over almost the entire upper left quadrant of the sun. NASA has described the giant gaping coronal gap as "extensive", "rotating our way" and bigger than anything they have seen in over a year.
This coronal hole is at least 400,000 miles across, which is more than 50 Earths side by side.
NASA's Skylab first spotted coronal holes in the early 1970s.
According to NASA, their size and number varies in concert with the sun's solar cycle, which reaches a maximum of activity approximately every 11 years. Late 2013 or early 2014, as the sun will head toward the maximum, the coronal holes move closer and closer to the sun's poles.
NASA will study the mysteries of the sun, yet many things to unveil.
IRIS will open doors for new discoveries. Using spectrometry and imaging, IRIS will trace the flow of energy and plasma through the chromospheres and transition region into the sun's corona.
NASA said:
"The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate."
Massive Coronal Hole on the Sun
NASA's Solar Dynamics Observatory captured this picture of the sun on June 18, 2013, showing a huge coronal hole – seen here in dark blue - spread out over almost the entire upper left quadrant of the sun. A coronal hole is an area of the sun's atmosphere, the corona, where the magnetic field opens up and the material flows quickly out. This results in a cooler and less dense atmosphere than the surrounding areas. This coronal hole is at least 400,000 miles across, which is more than 50 Earths side by side. Coronal holes spew out fast solar wind, probably traveling at about 400-500 miles per second. This is roughly twice the speed of the normal solar wind, the solar material that is constantly streaming off the sun in every direction to fill the solar system.
Coronal holes were first spotted by NASA's Skylab in the early 1970s. Scientists now know that their size and number varies in concert with the sun's solar cycle, which reaches a maximum of activity approximately every 11 years. Every time the sun heads toward that maximum, currently expected for late 2013 or early 2014, the coronal holes move closer and closer to the sun's poles.
This image of the sun from June 18, 2013, shows a coronal hole – that is, an area of cooler, less dense material in the sun's atmosphere, the corona - in the upper left side, represented in blue. In this image from NASA's Solar Dynamics Observatory, the blue color represents light in the 171 Angstrom wavelength, which shows the coolest material present in the image. Two other wavelengths of light are also shown in the picture: 211 Angstroms, in red, and 193 Angstroms in brown. Credit: NASA/SDO
Coronal holes were first spotted by NASA's Skylab in the early 1970s. Scientists now know that their size and number varies in concert with the sun's solar cycle, which reaches a maximum of activity approximately every 11 years. Every time the sun heads toward that maximum, currently expected for late 2013 or early 2014, the coronal holes move closer and closer to the sun's poles.
This image of the sun from June 18, 2013, shows a coronal hole – that is, an area of cooler, less dense material in the sun's atmosphere, the corona - in the upper left side, represented in blue. In this image from NASA's Solar Dynamics Observatory, the blue color represents light in the 171 Angstrom wavelength, which shows the coolest material present in the image. Two other wavelengths of light are also shown in the picture: 211 Angstroms, in red, and 193 Angstroms in brown. Credit: NASA/SDO
Page Last Updated: June 28th, 2013
Page Editor: NASA Administrator
NASA Official: Brian Dunbar
Page Editor: NASA Administrator
NASA Official: Brian Dunbar
July 20, 2013
Image of the Day: Gigantic Coronal Hole Found Hovering Over Sun's North Pole
The European Space Agency/NASA Solar and Heliospheric Observatory, or SOHO, captured this image of a gigantic coronal hole hovering over the sun’s north pole on July 18, 2013, at 9:06 a.m. EDT. Coronal holes are dark, low density regions of the sun’s outermost atmosphere, the corona. They contain little solar material, have lower temperatures, and therefore, appear much darker than their surroundings.
Coronal holes are a typical feature on the sun, though they appear at different places and with more frequency at different times of the sun’s activity cycle. The activity cycle is currently ramping up toward what is known as solar maximum, currently predicted for late 2013. During this portion of the cycle, the number of coronal holes decreases.
The Daily Galaxy via ESA&NASA/SOHO
During solar max, the magnetic fields on the sun reverse and new coronal holes appear near the poles with the opposite magnetic alignment. The coronal holes then increase in size and number, extending further from the poles as the sun moves toward solar minimum again. At such times, coronal holes have appeared that are even larger than this one.
The holes are important to our understanding of space weather, as they are the source of a high-speed wind of solar particles that streams off the sun some three times faster than the slower wind elsewhere. While it’s unclear what causes coronal holes, they correlate to areas on the sun where magnetic fields soar up and away, failing to loop back down to the surface, as they do elsewhere.
The Daily Galaxy via ESA&NASA/SOHO
Large Coronal Hole Near the Sun's North Pole
The European Space Agency/NASA Solar and Heliospheric Observatory, or SOHO, captured this image of a gigantic coronal hole hovering over the sun’s north pole on July 18, 2013, at 9:06 a.m. EDT. (Credit: ESA & NASA/SOHO)
July 19, 2013 — The European Space Agency/NASA Solar and Heliospheric Observatory, or SOHO, captured this image of a gigantic coronal hole hovering over the sun's north pole on July 18, 2013, at 9:06 a.m. EDT. Coronal holes are dark, low density regions of the sun's outermost atmosphere, the corona. They contain little solar material, have lower temperatures, and therefore, appear much darker than their surroundings.
Coronal holes are a typical feature on the sun, though they appear at different places and with more frequency at different times of the sun's activity cycle. The activity cycle is currently ramping up toward what is known as solar maximum, currently predicted for late 2013. During this portion of the cycle, the number of coronal holes decreases. During solar max, the magnetic fields on the sun reverse and new coronal holes appear near the poles with the opposite magnetic alignment. The coronal holes then increase in size and number, extending further from the poles as the sun moves toward solar minimum again. At such times, coronal holes have appeared that are even larger than this one.
The holes are important to our understanding of space weather, as they are the source of a high-speed wind of solar particles that streams off the sun some three times faster than the slower wind elsewhere. While it's unclear what causes coronal holes, they correlate to areas on the sun where magnetic fields soar up and away, failing to loop back down to the surface, as they do elsewhere.
The holes are important to our understanding of space weather, as they are the source of a high-speed wind of solar particles that streams off the sun some three times faster than the slower wind elsewhere. While it's unclear what causes coronal holes, they correlate to areas on the sun where magnetic fields soar up and away, failing to loop back down to the surface, as they do elsewhere.
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