A team of astronomers using NASA’s three Sun-gazing spacecraft – Solar and Heliospheric Observatory (SOHO), Solar Terrestrial Relations Observatory (STEREO) and Solar Dynamics Observatory (SDO) – has spotted unusual eruptions in which a series of fast puffs forced the slow ejection of a massive burst of plasma from the outermost atmosphere of the Sun. The eruptions took place over a period of three days, starting on January 17, 2013.
This combination of three wavelengths of light from NASA’s SDO shows one of the multiple jets that led to a series of slow coronal puffs on January 17, 2013. The light has been colorized in red, green and blue. Image credit: Nathalia Alzate / SDO.
The Sun’s outermost atmosphere, the corona, is made of plasma that has a temperature of millions of degrees and extends millions of kilometers into space.
On January 17, 2014, the SOHO spacecraft observed puffs emanating from the base of the corona and rapidly exploding outwards into interplanetary space.
The puffs occurred roughly once every 3 hours. After about 12 hours, a much larger eruption of material began, apparently eased out by the smaller-scale explosions.
By looking at high-resolution images taken by SDO and STEREO observatories over the same time period and in different wavelengths, the team could focus on the cause of the puffs and the interaction between the small and large-scale eruptions.
“Looking at the corona in extreme UV-light we see the source of the puffs is a series of energetic jets and related flares,” said team leader Dr Nathalia Alzate from the University of Aberystwyth in Wales, who reported the results at the 2014 Royal Astronomical Society’s National Astronomy Meeting in Portsmouth, England, on June 23.
“The jets are localized, catastrophic releases of energy that spew material out from the sun into space. These rapid changes in the magnetic field cause flares, which release a huge amount of energy in a very short time in the form of super-heated plasma, high-energy radiation and radio bursts.”
“The big, slow structure is reluctant to erupt, and does not begin to smoothly propagate outwards until several jets have occurred,” Dr Alzate said.
Because the events were observed by multiple spacecraft, each viewing the Sun from a different perspective, the scientists were able to resolve the 3D configuration of the eruptions.
This allowed them to estimate the forces acting on the slow eruption and discuss possible mechanisms for the interaction between the slow and fast phenomena.
“We still need to understand whether there are shock waves, formed by the jets, passing through and driving the slow eruption, or whether magnetic reconfiguration is driving the jets allowing the larger, slow structure to slowly erupt. Thanks to recent advances in observation and in image processing techniques we can throw light on the way jets can lead to small and fast, or large and slow, eruptions from the Sun,” Dr Alzate said.
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Nathalia Alzate et al. Interaction between Dense Coronal Material and Multiple Impulsive Events. Royal Astronomical Society’s National Astronomy Meeting, June 23, 2014
