First Year In Space For NASA’s IRIS Solar Observatory
[ Watch The Video: A First For IRIS: Observing A Gigantic Solar Eruption ]
Karen C. Fox, NASA
On June 27, 2013, NASA’s newest solar observatory was launched into orbit around Earth. The Interface Region Imaging Spectrograph, or IRIS, observes the low level of the sun’s atmosphere — a constantly moving area called the interface region — in better detail than has ever been done before.
During its first year in space, IRIS provided detailed images of this area, finding even more turbulence and complexity than expected. The interface region lies at the core of many outstanding questions about the sun’s atmosphere, such as how solar material in the corona reaches millions of degrees, several thousand times hotter than the surface of the sun itself or how the sun creates giant explosions like solar flares and coronal mass ejections. The interface region is also where most of the ultraviolet emission is generated that impacts the near-Earth space environment and Earth’s climate.
In its first year, IRIS fortuitously witnessed dozens of solar flares, including one X-class flare, and the foot points of a coronal mass ejection, or CME. IRIS must commit to pointing at certain sections of the sun at least a day in advance, so catching these eruptions in the act involves educated guesses and a little bit of luck.
The IRIS instrument captures two kinds of data on all its observations: IRIS collects both images of the sun and a kind of data called spectra. A spectrograph splits the light from a given point on the sun into its discrete wavelengths – a technique that ultimately allows scientists to measure temperature, velocity and density of the solar material behind the slit. When looking at the onset of a flare or at the foot points of a CME, therefore, scientists can parse out how the material moves, and shed light on what causes these eruptions.
The spectra are a crucial tool in the IRIS arsenal to understand the interface region. The solar material there is relatively dense and giant swaths of material roil up and down. Figuring out how the material moves and heats up provides information about how energy courses through the region, changing along the way between heat, movement and magnetic energy. One of the first science papers published with IRIS data used these spectra to provide unique, faster-than-ever characterization of how solar material in sunspots follows a repeated pattern of quick heating while accelerating upward, followed by an even faster rebound downward. This oscillation has been seen before, but never with the quick time cadence that is IRIS’ hallmark.
Scientists are in the process of analyzing the data from IRIS’s first year, and will have more results to share shortly. The prime mission lasts until summer 2015. Lockheed Martin’s Solar & Astrophysics Laboratory, Palo Alto, California, designed and manages the mission. The Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, built the telescope. Montana State University in Bozeman, Montana. helped design the spectrograph. NASA’s Ames Research Center in Moffett Field, California, provides mission operations and ground data systems. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the Small Explorer Program for NASA’s Science Mission Directorate in Washington, D.C. The Norwegian Space Centre provides regular downlinks of science data. Other contributors include the University of Oslo and Stanford University in Stanford, California.