NASA’s IRIS Helps Explain Mysterious Heating of the Solar Atmosphere

NASA’s newest sun-watcher, the Interface Region Imaging Spectrograph, launched in 2013 with a specific goal: track how energy and heat coursed through a little understood region of the sun called the interface region. Sandwiched between the solar surface and its outer atmosphere, the corona, the interface region is where the cooler temperatures of the sun’s surface transition to the hotter temperatures above. Moreover, all the energy to power the sun’s output — including eruptions such as solar flares and the sun’s constant outflow of particles called the solar wind — must make its way through this region.

Five papers based on IRIS data will highlight different aspects of the energy’s journey from the sun’s surface through its atmosphere in the Oct. 17, 2014, issue of Science magazine. By looking at various regions of the interface region in unprecedented resolution, the papers offer clues to what heats the corona to unexplained temperatures of millions of degrees, far hotter than the surface of the sun itself, as well as what causes great writhing movement and accelerated particles throughout the solar atmosphere.

“This set of 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 Bart De Pontieu the 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.”

Solar Heat Bombs

One of the biggest surprises comes in the form of heat pockets of 200,000 F, low in the solar atmosphere – far lower down than where such high temperatures were expected. In a paper led by Hardi Peter of the Max Planck Institute for Solar System Research in Gottingen, Germany, the pockets were named bombs because of how much energy they release in such a short time.

Bright lights in this movie from NASA’s IRIS, represents spots of intense heat — at 200,000 F — that may hold clues to what heats the solar atmosphere to mysteriously high temperatures.
Image Credit: NASA/IRIS/Peter

Identifying different temperature material in the solar atmosphere is fairly straightforward, but it is much more complex to determine how high above the surface such material lies. Spotting such features relied heavily on IRIS’ high-resolution spectrograph, an instrument that divides incoming light into its separate wavelengths. Such spectra can then be analyzed to see what temperature material is present in a given area as well as how dense it is and how fast it is moving. IRIS showed this very hot material sandwiched between two cold layers at temperatures usually found only near the sun’s surface, thus giving information about its low-lying location that would have been otherwise hard to find…. Continue reading NASA’s IRIS Helps Explain Mysterious Heating of the Solar Atmosphere

IRIS: Observing a Gigantic Solar Eruption

A coronal mass ejection burst off the side of the sun on May 9, 2014. The giant sheet of solar material erupting was the first CME seen by NASA’s Interface Region Imaging Spectrograph, or IRIS. The field of view seen here is about five Earth’s wide and about seven and a half Earth’s tall.

IRIS must commit to pointing at certain areas of the sun at least a day in advance, so catching a CME in the act involves some educated guesses and a little bit of luck.

Video: Coronal Hole Squared

A NASA spacecraft has made a surprising find on the surface of the sun: a square-shaped “hole” in the star’s outer atmosphere.

The dark square on the sun, known as a “coronal hole,” is an area where the solar wind is streaming out of the sun at superfast speeds. NASA captured a video of the sun’s square-shaped coronal hole between Monday and Wednesday (May 5-7) using the powerful Solar Dynamics Observatory (SDO).

The coronal hole appears dark in the NASA view because there is less material emitting light in the ultraviolet range of the spectrum used to make the video, according to a NASA video description. [Biggest Solar Storms of 2014 (Photos)]

“Inside the coronal hole you can see bright loops where the hot plasma outlines little pieces of the solar magnetic field sticking above the surface,” SDO officials wrote in the video description. “Because it is positioned so far south on the sun, there is less chance that the solar wind stream will impact us here on Earth.”

NASA’s sun-watching Solar Dynamics Observatory is just one of a fleet of spacecraft keeping a close watch on the weather on Earth’s parent star. In 2013, the sun experienced its peak activity of its 11-year solar weather cycle.

Engineers work with the IRIS spacecraft on the nose of the Pegasus XL rocket that will launch the solar observatory into Earth orbit. Photo credit: VAFB/Rnady Beaudoin

IRIS to Take Precise Look at Sun’s Energy

Engineers work with the IRIS spacecraft on the nose of the Pegasus XL rocket that will launch the solar observatory into Earth orbit. Photo credit: VAFB/Rnady Beaudoin

Engineers work with the IRIS spacecraft on the nose of the Pegasus XL rocket that will launch the solar observatory into Earth orbit. Photo credit: VAFB/Rnady Beaudoin

By Steven Siceloff,
NASA’s Kennedy Space Center

Researchers hope NASA’s latest solar observatory will answer a fundamental question of how the sun creates such intense energy.

Scheduled to launch June 27, the IRIS spacecraft will point a telescope at the interface region of the sun that lies between the surface and the million degree outer atmosphere called the corona. It will improve our understanding of how energy moves from the sun’s surface to the glowing corona, heating up from 6,000 degrees to millions of degrees.

The IRIS mission, short for Interface Region Imaging Spectrograph, calls for the 7-foot-long spacecraft to point its ultraviolet telescope at the sun to discern features as small as 150 miles across. It will look at about 1 percent of the sun’s surface.

“IRIS will show the solar chromosphere in more detail than has ever been observed before,” said Adrian Daw, deputy project scientist. “My opinion is that we are bound to see something we didn’t expect to see.”

IRIS is a NASA Small Explorer that will complement the Solar Dynamics Observatory and Hinode missions to explore how the solar atmosphere works and impacts Earth. SDO and Hinode will monitor the solar surface and outer atmosphere, with IRIS watching the region in between.

“IRIS almost acts as a microscope to SDO’s telescope,” said Jim Hall, mission manager for IRIS. “It’s going to look in closely and it’s going to look at that specific region to see how the changes in matter and energy occur in this region. It’s going to collectively bring us a more complete view of the sun.” IRIS improves our understanding of the interface region where most of the sun’s ultraviolet emission is generated that impacts the near Earth space environment and Earth’s climate. Solar activity such as coronal mass ejections and solar flares, also are of great interest to spacecraft designers who have to figure out ways to protect instruments and electronics from them.

“We’re always looking for the answers to why and everything starts at the root with the sun,” Hall said.

IRIS will ride into Earth orbit on an Orbital Sciences Pegasus XL rocket. The Pegasus is famous as the only winged launcher in NASA’s inventory. Though small compared to the gigantic boosters that send heavy satellites into orbit and probes to distant worlds, the Pegasus’ size and flexibility has allowed numerous missions to be launched that would have been too small for larger rockets.

“Pegasus has been a tremendously successful launch vehicle for NASA,” said Tim Dunn, launch director for IRIS. “We have launched 18 successful missions on Pegasus. The team is very dynamic, very flexible. They’re able to accomplish a tremendous amount in a very short time.”

The Pegasus and its IRIS payload will be carried to about 39,000 feet under a modified L-1011 airliner taking off from Vandenberg Air Force Base in California. Over the Pacific Ocean off the California coast, the plane will drop the Pegasus to begin the launch.

The Pegasus will ignite its solid-fueled first stage five seconds into its fall and arch skyward with the main wing giving it lift and the three fins in the back steering it through the thick layers of Earth’s lower atmosphere.

The rocket will burn its load of fuel in 73 seconds and fall away. The second stage, which has no wings, will ignite 94 seconds into flight and push IRIS higher and faster into space. The third stage will take over after that, delivering IRIS into its orbit about 10 minutes after launch.

This is the last one scheduled for the Pegasus rocket because there are not any small spacecraft missions that fit the Pegasus niche.

The launch is taking place from the West Coast because IRIS will go into a roughly polar orbit, meaning it will cross over the north and south pole regions of Earth on each pass around the planet.

“Eight months out of the year, we are freely viewing the sun in that orbit,” Hall said.

Once IRIS is in space with its solar panels unfolded to provide electricity and the telescope flipped open, scientists expect to see intriguing data pretty quickly.

“I think the biggest surprise will come once the mission is launched and it starts to observe the sun,” Daw said. “We know to some extent what we hope to learn, what specific science questions we are going to answer, but there’s always that element of surprise.”


Van Gogh Sun

A crucial, and often underappreciated, facet of science lies in deciding how to turn the raw numbers of data into useful, understandable information — often through graphs and images. Such visualization techniques are needed for everything from making a map of planetary orbits based on nightly measurements of where they are in the sky to colorizing normally invisible light such as X-rays to produce “images” of the sun.

More information, of course, requires more complex visualizations and occasionally such images are not just informative, but beautiful too.

Such is the case with a new technique created by Nicholeen Viall, a solar scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. She creates images of the sun reminiscent of Van Gogh, with broad strokes of bright color splashed across a yellow background. But it’s science, not art. The color of each pixel contains a wealth of information about the 12-hour history of cooling and heating at that particular spot on the sun. That heat history holds clues to the mechanisms that drive the temperature and movements of the sun’s atmosphere, or corona.

To look at the corona from a fresh perspective, Viall created a new kind of picture, making use of the high resolution provided by NASA’s Solar Dynamics Observatory (SDO). SDO’s Atmospheric Imaging Assembly (AIA) provides images of the sun in 10 different wavelengths, each approximately corresponding to a single temperature of material. Therefore, when one looks at the wavelength of 171 Angstroms, for example, one sees all the material in the sun’s atmosphere that is a million degrees Kelvin. By looking at an area of the sun in different wavelengths, one can get a sense of how different swaths of material change temperature. If an area seems bright in a wavelength that shows a hotter temperature an hour before it becomes bright in a wavelength that shows a cooler temperature, one can gather information about how that region has changed over time.

Viall’s images show a wealth of reds, oranges, and yellow, meaning that over a 12-hour period the material appear to be cooling. Obviously there must have been heating in the process as well, since the corona isn’t on a one-way temperature slide down to zero degrees. Any kind of steady heating throughout the corona would have shown up in Viall’s images, so she concludes that the heating must be quick and impulsive — so fast that it doesn’t show up in her images. This lends credence to those theories that say numerous nanobursts of energy help heat the corona.

Sunspot AR 1476: It can be seen in the upper left of this picture - and could unleash gigantic solar flares

The ‘monster’ sunspot AR 1476

Heat is on: ‘Monster’ sunspot could put Earth in the crosshairs of powerful solar storms

Sunspot AR 1476: It can be seen in the upper left of this picture – and could unleash gigantic solar flares

It could result in a gigantic coronal mass ejection, which would blast the Earth with radiation and possibly knock-out power lines and disrupt satellites…
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