Sun Coronal Cells

Scientists at the U.S. Naval Research Laboratory (NRL) in Washington, D.C., discovered the

odd, newly identified features, which they call coronal cells, by studying the sun’s ultraviolet emissions at temperatures around 1.8 million degrees Fahrenheit (999,700 degrees Celsius). According to reserachers the pattern of cells, which have bright centers and dark boundaries, look similar to bubbles that rise to the top of boiling water. But, the scientists were surprised to find these features higher up in the corona, a part of the sun’s atmosphere that is typically dominated by bright loops and dark coronal holes. Coronal holes are gaps in the sun’s magnetic field that punch holes in the corona, allowing gas and solar material to escape into space. Neil Sheeley and Harry Warren, two researchers in NRL’s space science division, examined time-lapse images of the sun from June 2011 and followed these coronal cells as they were carried across the solar disk by the sun’s 27-day rotation. They think that coronal cells look like flames shooting up, like candles on a birthday cake. When you see them from the side, they look like flames. When you look at them straight down, they look like cells. Sheeley and Warren used data from NASA’s Solar Dynamics Observatory (SDO), the agency’s twin Stereo probes, the Solar and Heliospheric Observatory (SOHO), and Japan’s sun-watching Hinode spacecraft to study these new solar features. The various spacecraft enabled them to study the coronal cells from multiple angles at the same time. Coronal cells are found in areas between coronal holes and so-called filament channels that separate sections of upward-pointing magnetic fields and their downward-pointing counterparts. Understanding how coronal cells form and grow could give scientists new insights into the magnetic structure of the sun’s corona, and how these cells affect the steady stream of solar material, known as the solar wind, that seeps from these holes. Sheeley and Warren superimposed images of the coronal cells on images of the sun’s magnetic field to study their placement over the surface of the sun. They found that the magnetic field bundles lay centered inside the cells. The researchers also found that coronal cells were consistently found in regions dominated by magnetic field lines that point in a single direction (either up or down). They also noticed that when magnetic fields of the nearby coronal holes and the coronal cells were intricately tied. When the fields of the coronal hole were open, extending far into space without returning to the sun, the field lines in the cells were closed. The opposite was also true, the researchers added.