July 2, 2012
Images Of Extreme Solar Activity Provide Origins Of Powerful Space Storms
Lawrence LeBlond for redOrbit.com - Your Universe Online
An international team of scientists have for the first time captured and identified images of an upward surge of the Sun´s gases into quiescent coronal loops, a discovery that provides one more step in the understanding of the origins of extreme storms in outer space, which are known to wreak havoc on satellite systems and power grids here on Earth.
University of Cambridge researchers worked with colleagues from the India and the US in imaging and visualizing the movement of gases at a million degrees in coronal loops -- solar structures that are rooted at both ends and extend out from the active regions of the Sun. These active regions are the “cradle” for explosive energy releases such as solar flares and coronal mass ejections (CME).
Scientists are hoping by observing these upward surges they will gain a better understanding of one of the most challenging issues in astrophysics -- how solar structures are heated and maintained in the upper solar atmosphere.
Solar activity is cyclical and the next maximum forecast should occur in May 2013. Such severe space weather is detrimental to Earth´s communications and electrical systems, and the UK currently lists this severity as very high in the 2012 National Risk Register of Civil Emergencies.
The Hinode Satellite, a joint project by Japanese, American, and European space agencies, was utilized to make the observations, which provided the first evidence of plasma upflows traveling at more than 10 miles per second in the one-million-degree active region loops. The team believes the upflow of gases is the result of “impulsive heating” close to the starting point regions of the loops.
“Active regions are now occurring frequently across the Sun. We have a really great opportunity to study them with solar spacecraft, such as Hinode and the Solar Dynamics Observatory (SDO),” said co-author Dr Helen Mason from the University of Cambridge´s Department of Applied Mathematics and Theoretical Physics. “Probing the heating of the Sun´s active region loops can help us to better understand the physical mechanisms for more energetic events which can impinge on the Earth´s environment.”
NASA´s SDO has shown large loops of hot gas guided by the Sun´s magnetic field in previous images, but the question has remained as to how solar plasma is heated and rises up into the loops in the first place.
They have now been able to answer that question, as their research provides the first visualization of plasma flow by showing the movement of gases within the loop with diagnostic imaging using the extreme ultraviolet imaging spectrometer (EIS) on the Hinode satellite. The spectrometer produces spectral lines that identify the horde of elements and ions within the loop and shifts in the position of the lines provide information on the motion of the plasma.
Although helium and hydrogen make up the bulk of the Sun´s composition, there are also a number of other trace elements, including oxygen and iron, as were observed in the hot ionized gas within the loops.
This gas may be caused by a process of “chromospheric evaporation” in which “impulsive heating” on a small scale can result in the heating of the solar active regions but on a larger scale can lead to solar flares, coronal mass ejections, and other huge explosions, according to the team of researchers.
“It is believed that magnetic energy builds up in an active region as the magnetic field becomes distorted, for example by motions below the surface of the Sun dragging the magnetic fields around,” explained Mason, whose study was published today in Astrophysical Journal Letters. “Sometimes magnetic flux can emerge or submerge and affect the overlying magnetic field. We believe that solar plasma surges upwards when impulsive heating results from magnetic reconnection which occurs either in the loops or close to the Sun´s surface.”
“The Sun governs the environment in which we live and it is the so-called solar active regions that drive extreme conditions leading to the explosive flares and the huge eruptions,” said Professor Richard Harrison MBE, Head of Space Physics and Chief Scientist at the STFC Rutherford Appleton Laboratory, who was not involved in the research. “Understanding these active regions is absolutely critical for the study of what we now call space weather. The work published by in this paper is a key element of that work, applying innovative analyses to the observations from the UK-led Hinode/EIS instrument.”
With better understanding of these active regions, scientists hope that one day they will be able to identify the magnetic field structures that lead to explosive solar energy releases and use this to better predict when such events will occur.
The Cambridge study was partially funded by the UK´s Science and Technology Facilities Council (STFC).