The Sun has a very dynamic atmosphere, with huge fountains of hot gas erupting in the atmosphere, or corona, every few minutes, travelling at tens of thousands of kilometers per hour and reaching great heights.

A team of scientists using the Hinode spacecraft has been searching for the origin and driver of these 'fountains', immense magnetic structures that thread through the solar atmosphere. On Wednesday 2 April at the Royal Astronomical Society National Astronomy Meeting in Belfast (NAM 2008), team leader Dr. Michelle Murray from the Mullard Space Science Laboratory (MSSL, University College London) presented the latest results from Hinode together with computer simulations that model conditions on the Sun.



During a total solar eclipse the Moon passes in front of the Sun, blocking out the most intense solar light and allowing us to view the Sun's atmosphere, or corona, from Earth. The Sun's light can be seen streaming through the immense magnetic structures that thread through the corona and stretch out into space. Image credit: Luc Viatour GFDL/CC

Since its launch in October 2006, scientists have been using Hinode to examine the solar atmosphere in extraordinary detail. One of the instruments on the space observatory, the Extreme Ultraviolet Imaging Spectrometer (EIS), generates images of the Sun and gives information on how fast its gases are moving.

Increases in pressure at the base of the Sun's magnetic field cause enormous jets of hot gas to shoot upwards into the solar atmosphere. Once the pressure ceases, the hot gases stop soaring into the atmosphere and fall back towards the solar surface. The changes in pressure are caused by rearrangements of the Sun's magnetic field, a continual process that results in looping cycles of increasing and decreasing pressure and, consequentially, intermittent solar fountains.



At the northern pole of the Sun, an incredibly fast fountain of hot gases shoots above the edge of the solar disk into the atmosphere before falling back down to the surface. In the foreground, gases bubble away at temperatures approaching millions of degrees Celsius. This movie was assembled from images captured with the EIS instrument, aboard the Hinode spacecraft, on 1 April 2007. Movie: Jian Sun / MSSL / UCL / JAXA / NAOJ / NASA / ESA / NSC

“EIS has observed the Sun's fountains in unprecedented detail and it has enabled us to narrow down the fountains' origins for the first time”, commented team member Deb Baker.

“We have also been able to find what drives the fountains by using computer experiments to replicate solar conditions.”

“The computer experiments demonstrate that when a new section of magnetic field pushes through the solar surface it generates a continual cycle of fountains”, explains Dr Murray, “but new magnetic fields are constantly emerging across the whole of the solar surface and so our results can explain a whole multitude of fountains that have been observed with Hinode.”