Scientists have obtained the sharpest view yet of features in the Sun's atmosphere using an experimental camera launched on a short-lived rocket. The system returned just five minutes of data, but this was enough to identify a fascinating new phenomenon the researchers refer to as "sparkles". These are bright points which appeared along magnetic field lines where huge amounts of energy are released.
It may help to explain how the Sun's outer atmosphere, or corona, is so much hotter than the star's surface known as photosphere. "The corona is millions of degrees hotter, and this has been a decades' long puzzle," said Prof Robert Walsh from the University of Central Lancashire. "The sparkles, we actually call them extreme ultraviolet dots, we believe are evidence of very localised but frequent energy release that could build up and heat the corona very easily," he said.
Pictures of the dots were acquired using NASA's High Resolution Coronal Imager (Hi-C). This is a next-generation instrument that was tested briefly on a sounding rocket, a small vehicle that takes a payload into space for just a few minutes before falling back down. The intention was to validate the design concept and performance of Hi-C so that it can be put forward for a future orbital mission. The instrument was directed to look at an active region in the middle of the Sun. As well as the sparkles, it saw huge clumps of charged gas racing along "highways" sculpted by the star's magnetic field.
This speeding material was moving inside a so-called solar filament, a prominence of dense plasma which can erupt outwards from the Sun. "The plasma was moving in opposite directions, back and fore, like on a motorway," said Prof Walsh. "We've never seen that before and that gives us an idea about the fundamental scale in the filaments." The sparkles themselves were off to the left of the filament in a region of twisted magnetic field lines.
The dots were sporadic and lasted about 25 seconds, although they appeared small on the scale of the Sun, they were immense. But it is the energy released by the sparkles that is really impressive. The team calculates it to be at least one million, million, million, million Joules in each dot. "Consider the consumption of energy in the UK in an entire year, it gets released in one of these dots in about 20-30 seconds," explained Prof Walsh. "When you add that up all over the surface of the Sun you are talking about something that could easily tackle the coronal heating problem. But to pin this down we'd have to fly Hi-C on a satellite."
NASA's Marshall Space Flight Center led the Hi-C launch with partners which included the Smithsonian Astrophysical Observatory, Lockheed Martin's Solar Astrophysical Laboratory, UClan, and the Lebedev Physical Institute of the Russian Academy of Sciences. The UK NAM runs all week at the University of St Andrews.