Source of dangerous high energy particles located in the sun

The source of potentially dangerous solar particles, released by the Sun at high speed during storms in its outer atmosphere, was first located by researchers at UCL and George Mason University, Virginia, USA .

These particles are highly charged and, if they reach Earth’s atmosphere, can potentially disrupt satellites and electronic infrastructure, as well as pose a radiation hazard to astronauts and aircraft passengers. In 1859, during what is known as the Carrington Event, a large solar storm caused the failure of telegraph systems across Europe and America. With the modern world being so dependent on electronic infrastructure, the risk of harm is much greater.

To minimize the danger, scientists are looking to understand how these particle fluxes are produced in order to better predict when they might affect Earth.

In the new study, published in Scientific progress, the researchers analyzed the composition of solar energy particles heading towards Earth and found that they had the same “fingerprint” as the plasma at the bottom of the Sun’s corona, near the middle region of the Sun. atmosphere of the Sun, 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 on the Sun originate. of plasma kept low in the solar atmosphere by powerful magnetic fields, these energetic particles, once released, are then accelerated by flares that travel at a speed of a few thousand kilometers per second.

“Energetic particles can arrive on Earth very quickly, in a few minutes to a few hours, these events lasting several days. Currently, we can only provide predictions of these events as they occur, because there is It is very difficult to predict these events before they happen. By better understanding the Sun’s processes, we can improve forecasting so that when a major solar storm hits, we have time to act to reduce the risks.

Lead author Dr David Brooks (George Mason University and Honorary Associate Professor at UCL MSSL) said: “Our observations provide tantalizing insight into the provenance of the material that produces solar energy particles in a few events. of the last solar cycle. we are now starting a new solar cycle, and once it has started we will use the same techniques to see if our results are generally true or if these events are somehow unusual.

“We are fortunate in that our understanding of the mechanisms behind solar storms and solar energy particles is likely to advance rapidly over the next several years thanks to the data that will be obtained from two spacecraft – the Solar Orbiter of the ‘ESA and NASA’s Parker Solar Probe – which head closer to the Sun than any spacecraft.

In the study, the researchers used measurements from NASA’s Wind satellite, located between the Sun and Earth, to analyze a series of solar energy particle flows, each lasting at least a day, in January 2014. They compared this to spectroscopy data from the JAXA-driven Hinode spacecraft. (The EUV imaging spectrometer on board the spacecraft was built by UCL MSSL and Dr. Brooks is a member of the Japan Mission Operations Team.)

They found that solar energy particles measured by the Wind satellite had the same chemical signature – an abundance of silicon over sulfur – as plasma confined near the top of the Sun’s chromosphere. These locations were at the “foot points” of the hot coronal loops, that is, at the bottom of the magnetic field and plasma loops extending into the outer atmosphere of the Sun and vice versa.

Using a new technique, the team measured the intensity of the coronary magnetic field at these foot points and found it to be very high, in the range of 245 to 550 Gauss, confirming the theory. according to which plasma is held in the Sun’s atmosphere by strong magnetic fields. before its spacewalk.

Solar energy particles are released from the Sun and are accelerated by solar flares (large explosions) or coronal mass ejections – ejections of huge clouds of plasma and magnetic field. About 100 solar energy particle events occur each 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 different source than the slow solar wind (the origin of which is still debated), as they are confined under specific conditions in warm coronal loops to the heart of the source region. A faster solar wind is continuously emitted by the Sun; its encounter with the Earth’s atmosphere can generate the Northern Lights.

The high-energy particles released in January 2014 originated from a volatile region of the Sun that exhibited frequent solar flares and CMEs, and an extremely strong magnetic field. The region, known as 11944, was one of the largest active regions of the Sun at the time and was visible to observers on Earth as a sunspot – a dark spot on the surface of the sun.

A strong radiation storm alert was issued at the time by the NOAA / NWS Space Weather Prediction Center, but it is not known that the solar energy particle event caused a disturbance in the atmosphere. terrestrial, although the computer systems of the Hinode spacecraft itself have recorded several particle impacts. .

A measurement of the strength of the magnetic field in the 11944 region was taken in a separate study shortly after this period, and was one of the highest ever recorded in the Sun – 8.2 kg.