New light shed on explosive solar activity
3 Jul 2012
The first images of an upward surge of the Sun’s gases into quiescent coronal loops have been identified by an international team of scientists led by the UK. The discovery is one more step towards understanding the origins of extreme space storms, which can destroy satellite communications and damage power grids on Earth.
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Hot (one million degree) active region loops and, right, flows of solar plasma (blueshifts).
Credit: Left: SDO/AIA (NASA).
The study published by University of Cambridge scientists working with colleagues in India and the USA is the first to visualise the movement of gases at one million degrees in coronal loops – solar structures that are rooted at both ends and extend out from active regions of the Sun. Active regions are the ‘cradle’ for explosive energy releases such as solar flares and coronal mass ejections (CMEs).
The observation will help scientists understand what is considered to be one of the most challenging issues in astrophysics – how solar structures are heated and maintained in the upper solar atmosphere. Extreme solar activity can lead to severe space storms that interfere with satellite communications and damage electric power transmission grids on Earth. Solar activity is cyclical, with the next maximum forecast to occur around May 2013, and severe space weather is now listed very high on the UK’s 2012 National Risk Register of Civil Emergencies.
The work was based on observations from the Hinode Satellites the Extreme ultraviolet Imaging Spactrometer (EIS) which was designed and developed by an international team lead by the UCL’s Mullard Space Science Laboratory. The new findings provide the first evidence of plasma upflows travelling at around 20 km per second in the one million degree active region loops. The scientists suggest that the upflow of gases is probably the result of “impulsive heating” close to the footpoint 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 imainge on the Earth’s environment.”
This research provides the first visualisation of plasma flow by showing the movement of gases within the loop as ‘blueshifts’ in diagnostic images using EIS) on the Hinode satellite. Spectral lines produced by the spectrometer act like ‘fingerprints’ or the ‘bar code’ in a supermarket – the lines identify the multitude of elements and ions within the loop and shifts in the position of the lines provide information on the motion of the plasma. The scientists suggest that the gas movement is 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 huge explosions, such as solar flares or coronal mass ejections.
The researchers hope that a better understanding of active regions might one day help scientists to identify the magnetic field structures that lead to explosive solar energy releases and use this as a means for predicting when such events will occur.
For the full press release visit: http://www.cam.ac.uk/research/news/new-light-shed-on-explosive-solar-activity/attachment/260612_intensity-and-flow-in-an-active-region_small_credit-sdo_aia-nasa/
The study is published today in Astrophysical Journal Letters.
