September 28, 2013
Sunrise Mission Provides A Closer Look At Sun’s Chromosphere
April Flowers for redOrbit.com - Your Universe Online
In June 2013, the solar observatory Sunrise was carried aloft by a NASA scientific balloon. Three months later, scientists from the Max Planck Institute for Solar System Research in Germany have presented unique insights into a layer on the sun called the chromosphere. The images from Sunrise are the highest-resolution ultraviolet light images to date of this thin corrugated layer, which lies between the sun's visible surface and the sun's outer atmosphere, the corona.
In the chromosphere, the temperature rises from 6,000 K/10,340 F/5,272 C at the surface of the sun to about 20,000 K/ 35,540 F/19,730 C. This region of the sun is constantly in motion, with different temperatures of hot material mixed over a range of heights. These heights stretch from the sun's surface to many thousands of miles up. Further into the corona, the temperatures continue to rise and it is unknown what powers the rise in temperatures.
"In order to solve this riddle it is necessary to take as close a look as possible at the chromosphere – in all accessible wavelengths," said Sami Solanki, the principal investigator for Sunrise from the Max Planck Institute. To obtain the images, Sunrise used an instrument that was able to filter particular ultraviolet wavelengths of light that are only emitted from the chromosphere.
A complex picture of the chronosphere is painted by these extremely high-resolution images in this particular wavelength. Dark regions with a diameter of approximately 600 miles can be discerned where the sun is quiet and inactive. These dark regions are surrounded by bright rims. Enormous flows of solar material rising up from within the sun, cooling off and sinking down again create these patterns. Occasionally, bright points flash up that are spectacularly eye-catching - they are much richer in contrast in these ultraviolet images than have been seen before. Researchers believe these bright points are indications of a phenomenon called magnetic flux tubes. These are the building blocks of the sun's magnetic field, which is of particular interest to scientists as it is ultimately responsible for all of the dynamic activity we see on the sun.
"These first analyses are extremely promising," said Solanki. "They show that the ultraviolet radiation from the chromosphere is highly suitable for visualizing detailed structures and processes."
The Sunrise research team hopes that the next few months will provide further insights - and they are looking forward to collaborating with NASA's Interface Region Imaging Spectrograph, or IRIS mission. IRIS, which launched just weeks after Sunrise's mission ended, also studies the ultraviolet radiation from chromosphere and corona.
Image 2 (below): Two images of the chromosphere as captured by the Sunrise solar observatory that flew on a NASA balloon in July 2013. On the left a typical pattern can be seen: dark areas surrounded by bright rims. On the right, the images show bright, stretched structures on the edges of the darker sunspots. Image Credit: MPS