NASA SDO: IRIS captures New information about sun's atmosphere

NASA’s Solar Dynamics Observatory provided the outer image of a coronal mass ejection on May 9, 2014. 

The IRIS mission views the interface region that lies between the sun’s photosphere and corona in unprecedented detail for researchers to study.

Credit: NASA, Lockheed Martin Solar & Astrophysics Laboratory

NASA's Interface Region Imaging Spectrograph (IRIS) has provided scientists with five new findings into how the sun's atmosphere, or corona, is heated far hotter than its surface, what causes the sun's constant outflow of particles called the solar wind, and what mechanisms accelerate particles that power solar flares.

The new information will help researchers better understand how our nearest star transfers energy through its atmosphere and track the dynamic solar activity that can impact technological infrastructure in space and on Earth.

Details of the findings appear in the current edition of Science "On the prevalence of small-scale twist in the solar chromosphere and transition region"DOI: 10.1126/science.1255732

"These findings reveal a region of the sun more complicated than previously thought," said Jeff Newmark, interim director for the Heliophysics Division at NASA Headquarters in Washington.

"Combining IRIS data with observations from other Heliophysics missions is enabling breakthroughs in our understanding of the sun and its interactions with the solar system."

The first result identified heat pockets of 200,000 degrees Fahrenheit, lower in the solar atmosphere than ever observed by previous spacecraft.

Scientists refer to the pockets as solar heat bombs because of the amount of energy they release in such a short time.

Identifying such sources of unexpected heat can offer deeper understanding of the heating mechanisms throughout the solar atmosphere.

For its second finding, IRIS observed numerous, small, low lying loops of solar material in the interface region for the first time.

The unprecedented resolution provided by IRIS will enable scientists to better understand how the solar atmosphere is energized.

A surprise to researchers was the third finding of IRIS observations showing structures resembling mini-tornadoes occurring in solar active regions for the first time.

These tornadoes move at speeds as fast as 12 miles per second and are scattered throughout the chromosphere, or the layer of the sun in the interface region just above the surface.

These tornados provide a mechanism for transferring energy to power the million-degree temperatures in the corona.

Another finding uncovers evidence of high-speed jets at the root of the solar wind. The jets are fountains of plasma that shoot out of coronal holes, areas of less dense material in the solar atmosphere and are typically thought to be a source of the solar wind.

The final result highlights the effects of nanoflares throughout the corona. Large solar flares are initiated by a mechanism called magnetic reconnection, whereby magnetic field lines cross and explosively realign.

These often send particles out into space at nearly the speed of light. Nanoflares are smaller versions that have long been thought to drive coronal heating.

IRIS observations show high energy particles generated by individual nanoflare events impacting the chromosphere for the first time.

"This research really delivers on the promise of IRIS, which has been looking at a region of the sun with a level of detail that has never been done before," said De Pontieu, IRIS science lead at Lockheed Martin in Palo Alto, California.

"The results focus on a lot of things that have been puzzling for a long time and they also offer some complete surprises."

More Information
Science "On the prevalence of small-scale twist in the solar chromosphere and transition region"DOI: 10.1126/science.1255732

NASA STEREO: Giant Waves Reveal True Size of Sun's Atmosphere

These observations, taken by NASA's Solar Terrestrial Relations Observatory (STEREO) on Aug. 5, 2007, helped scientists define the outer limit of the sun's atmosphere.

Credit: NASA/STEREO

The sun's volatile atmosphere is even bigger than expected, a NASA spacecraft revealed through observations of gigantic waves.

While the sun itself is 864,938 miles (1.392 million kilometers) wide, NASA's Solar Terrestrial Relations Observatory (STEREO), found that the solar atmosphere, known as the corona, stretches 5 million miles (8 million km) above the sun's surface.

"We've tracked sound-like waves through the outer corona and used these to map the atmosphere," Craig DeForest of the Southwest Research Institute in Boulder, Colorado, said in a statement from NASA. "We can't hear the sounds directly through the vacuum of space, but with careful analysis we can see them rippling through the corona."



These waves, called magnetosonic waves, are a cross between sound waves and magnetic waves called Alfven waves.

They oscillate only about once every four hours and span 10 times the width of Earth, NASA officials said.

When magnetosonic waves erupt from solar storms and other disturbances, they can ripple up to 5 million miles away from the sun's surface, DeForest and colleagues found.

Beyond this boundary, solar material separates from the corona and flows out into space in a steady stream known as the solar wind.

NASA officials say the findings will help researchers prepare for the space agency's Solar Probe Plus mission, scheduled to launch in 2018.

That mission will send a spacecraft closer to the sun that any man-made object has ever ventured, within 4 million miles (6.4 million km) of the sun's surface.

Now, scientists know the probe will actually be traveling through the corona during its historic trip.

"This research provides confidence that Solar Probe Plus, as designed, will be exploring the inner solar magnetic system," Marco Velli, a Solar Probe Plus scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, said in a statement.

"The mission will directly measure the density, velocity and magnetic field of the solar material there, allowing us to understand how motion and heat in the corona and solar wind are generated."

The findings, which were published last month in The Astrophysical Journal, should also help astronomers define the inner boundary of the heliosphere, the giant bubble enveloping the solar system, created by the solar wind and solar magnetic field.

NASA SDO: Bright points in Sun's atmosphere mark patterns deep in its interior

Brightpoints in the sun's atmosphere, left, correspond to magnetic parcels on the sun's surface, seen in the processed data on the right. 

Green spots show smaller parcels, red and yellow much bigger ones. 

Credit: NASA/SDO

Like a balloon bobbing along in the air while tied to a child's hand, a tracer has been found in the sun's atmosphere to help track the flow of material coursing underneath the sun's surface.

New research that uses data from NASA's Solar Dynamics Observatory (SDO), to track bright points in the solar atmosphere and magnetic signatures on the sun's surface offers a way to probe the star's depths faster than ever before.

The technique opens the door for near real-time mapping of the sun's roiling interior – movement that affects a wide range of events on the sun from its 22-year sunspot cycle to its frequent bursts of X-ray light called solar flares.

"There are all sorts of things lurking below the surface," said Scott McIntosh, first author of a paper on these results in the April 1, 2014, issue of the Astrophysical Journal Letters.

"And we've found a marker for this deep rooted activity. This is kind of a gateway to the interior, and we don't need months of data to get there."

One of the most common ways to probe the sun's interior is through a technique called helioseismology in which scientists track the time it takes for waves – not unlike seismic waves on Earth—to travel from one side of the sun to the other.

From helioseismology solar scientists have some sense of what's happening inside the sun, which they believe to be made up of granules and super-granules of moving solar material.

The material is constantly overturning like boiling water in a pot, but on a much grander scale: A granule is approximately the distance from Los Angeles to New York City; a super-granule is about twice the diameter of Earth.

SDO contains three instruments; Helioseismic and Magnetic Imager (HMI), Atmospheric Imaging Assembly (AIA), and Extreme Ultraviolet Variablity Experiment (EVE) -- for observations leading to a more complete understanding of the solar dynamics that drive variability in the Earth's environment. 

Credit: NASA/Goddard Space Flight Center

Instead of tracking seismic waves, the new research probes the solar interior using the Helioseismic Magnetic Imager (HMI) on SDO, which can map the dynamic magnetic fields that thread through and around the sun.

Since 2010, McIntosh has tracked the size of different magnetically-balanced areas on the sun, that is, areas where there are an even number of magnetic fields pointing down in toward the sun as pointing out.

Think of it like looking down at a city from above with a technology that observed people, but not walls, and recording areas that have an even number of men and women.

Even without seeing the buildings, you'd naturally get a sense for the size of rooms, houses, buildings, and whole city blocks – the structures in which people naturally group.

More Information: 'Identifying Potential Markers of the Sun's Giant Convective Scale' Astrophysical Journal April 2014: Authors: Scott W. McIntosh, Xin Wang, Robert J. Leamon, and Philip H. Scherrer: doi:10.1088/2041-8205/784/2/L32