
A coronal mass ejection, or CME, that erupted into space on August 31, 2012. Pictured is a mixed version of the wavelengths of 171 and 304 angstroms from the Solar Dynamics Observatory. Note: the earth is not so close to the sun, this image is for scale purposes only. Credit: NASA / Goddard Space Flight Center
The source of potentially dangerous solar particles released at high speeds during storms in its outer atmosphere was first detected by researchers at UCL and George Mason University, Virginia, USA.
These particles are highly charged and could potentially disrupt satellites and electronic infrastructure if they reach Earth’s atmosphere, and also pose astronauts and aircraft for astronauts. In 1859, during the Carrington Event, a major solar storm caused telegraphic systems to fail in Europe and America. Because the modern world is so dependent on electronic infrastructure, the potential for damage is much greater.
To reduce the danger, scientists are trying to understand how these streams of particles are produced so that they can better predict when they may affect the earth.
In the new study, published in Scientific progress, researchers analyzed the composition of solar energy particles that were on their way to Earth and found that they have the same ‘fingerprint’ as plasma located low in the sun’s corona, near the central region of the sun’s atmosphere, the chromosphere.
Co-author Dr Stephanie Yardley (UCL Mullard Space Science Laboratory, MSSL) said: ‘In our study, we observed for the first time exactly where solar energy particles come from in the sun. Our evidence supports the theories that these highly charged particles come from plasma held low in the sun’s atmosphere by strong magnetic fields. Once these energetic particles are released, they are then accelerated by eruptions moving at a speed of several thousand kilometers per second.
‘Energetic particles can reach the earth quickly within a few minutes to a few hours, and these events take days. Currently, we can only provide predictions about these events, as it is very difficult to predict these events before they occur. By better understanding the sun’s processes, we can improve the forecasts so that we have time to act to reduce the risks when a major solar storm occurs. ā
Lead author Dr David Brooks (George Mason University and honorary associate professor at UCL MSSL) said: “Our observations provide a tantalizing look at where the materials that produce solar energy particles come from in some events from the last solar cycle. with a new solar cycle and once it is underway, we will use the same techniques to see if our results are generally true, or if these events are somehow unusual.
‘We are fortunate because our understanding of the mechanisms behind solar storms and solar energy particles is likely to progress rapidly in the coming years thanks to data obtained from two spacecraft – ESA’s Solar Orbiter and the NASA Parker Solar Probe – which is closer to the sun than any spacecraft before. ā
In the study, researchers used measurements from NASA’s Wind satellite, located between the sun and Earth, to analyze a series of solar energy particle currents, lasting at least a day, in January 2014. They compare it with the spectroscopy data of the JAXA-led Hinode spaceship. (The EUV Imaging Spectrometer aboard the spacecraft was built by UCL MSSL and Dr. Brooks is a member of the mission’s operational team in Japan.)
They found that the solar energy particles measured by the Wind satellite had the same chemical signature – an abundance of silicon compared to sulfur – since plasma near the top of the sun’s chromosphere is limited. These places were at the “foothills” of warm coronal loops – that is, at the bottom of the loops with magnetic field and plasma extending to the sun’s outer atmosphere and back again.
Using a new technique, the team measured the coronal magnetic field strength at these foothills and found that it was very high in the region of 245 to 550 Gauss, confirming the theory that the plasma passes through strong magnetic fields in the sun’s atmosphere. held. before its release into space.
Solar energy particles are released from the sun and are accelerated by solar flares (large explosions) or coronal mass ejections – ejections of large plasma clouds and magnetic field. Approximately 100 solar energy particle events occur every 11-year solar cycle, although this number varies from cycle to cycle.
The latest findings support the idea that some solar energy particles come from a source other than the slow solar wind (the origin of which is still debated), as it is limited in specific conditions in hot coronal loops in the core of the source region. A faster solar wind is continuously radiated by the sun; the encounter with the earth’s atmosphere can evoke the Northern Lights.
The high-energy particles released in January 2014 come from a volatile region of the sun with frequent solar flares and CMEs, and an extremely strong magnetic field. The region, known as 11944, was at that time one of the largest active regions on the Sun and was visible to observers on earth as a sunspot – a dark spot on the surface of the sun *.
The NOAA / NWS Space Weather Prediction Center at the time issued a strong warning for the radiation of the storm, but it is not known that the event of the solar energy particle caused any disruption in the Earth’s atmosphere, although computer systems on the Hinode spacecraft itself recorded several particle hits. .
A measurement was taken of the strength of the magnetic field in the region of 11944 in a separate study shortly after this period, and was one of the highest ever recorded in the sun – 8.2kG.
Reference: “The source of the most important solar energy particle events from the superactive region 11944” by David H. Brooks and Stephanie L. Yardley, March 3, 2021, Scientific progress.
DOI: 10.1126 / sciadv.abf0068