Uploaded by IwantToBelieve76 on 9 Apr 2012
Drs. Neil Sheeley and Harry Warren, researchers in NRL’s Space Science Division, describe these Coronal Cells as appearing in discrete bundles “like candles on a birthday cake.” The researchers discovered the cells in ultraviolet emission lines formed at temperatures around one-million degrees Kelvin. Although the researchers made their discovery using high-resolution images from the Atmospheric Imaging Assembly aboard the Solar Dynamics Observatory (SDO), they also observed the cells on ultraviolet images from STEREO-A and -B spacecraft recently, and from the Solar and Heliospheric Observatory (SOHO) in 2000 near the previous sunspot maximum. In addition, they used Doppler images, constructed from the Extreme-Ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft, to deduce that the outflow is faster at the centers of the cells than at their boundaries.
The researchers used time-lapse sequences of Fe XII 193 Å coronal images to follow these special regions as they were carried across the solar disk by the 27-day solar rotation. Near disk center, the Coronal Cells looked like photospheric granules with bright centers and dark, narrow intercellular lanes. But their 30,000 kilometer diameters were much larger than the 1,000 km dimension of granules. A comparison with magnetic maps of the photosphere, obtained with the Helioseismic Magnetic Imager aboard SDO, showed that the cells were centered on unipolar flux concentrations, but left doubt about whether the cellular emission was coming from the tops of closed loops near the Sun’s surface, or from longer field lines that extend higher into the corona. This question was answered when observations were obtained away from disk center. Here, the cells appeared as long plumes of emission projecting toward the nearest solar limb. Moreover, simultaneous observations from the STEREO-B and SDO spacecraft, separated by about 90 degrees along Earth’s orbit around the Sun, showed the same plumes projecting in opposite directions. Such stereoscopic views left no doubt that the Coronal Cells are columns of emission extending radially outward through the lower corona, like candles on a birthday cake.