For the first time in the world, Russian scientists have described in detail how prominences—ejections of hot solar matter that are far from the surface of a star—are heated. Studying this phenomenon will help predict the speeds of particles in outer space and their impact on the Earth’s magnetosphere. The specialists achieved their achievement thanks to the Siberian Radioheliograph, a new mega-installation that allows observing the Sun in the radio range with high resolution. Experts noted that studying such phenomena is important for predicting space weather.
How does a radio telescope work?
Irkutsk scientists from the Institute of Solar-Terrestrial Physics (ISTP) of the Siberian Branch RAS have made a discovery that sheds light on an important mystery of the Sun. They explained how prominences—ejections of hot solar matter—heat away from the Earth’s surface. According to the researchers, studying this phenomenon will help predict the speed of particles in outer space and their impact on the planet’s magnetosphere. It is also involved in the transfer of energy from the relatively cold surface of the star, where the temperature is about 6 thousand degrees, to the corona, where it is more than 1 million degrees.
The discovery was made thanks to a unique astrophysical instrument – the Siberian radioheliograph, which is located at the Badary observatory in the Tunkinskaya Valley near Lake Baikal.
This solar telescope consists of 526 dish antennas and observes the star at different frequencies of radio waves. As scientists noted, the physical parameters of the mega-installation make it possible to “see” the Sun both as a whole and individual phenomena that occur on it. Moreover, the spatial, temporal and frequency resolution of the Siberian radio telescope make it the best instrument in its class in the world.
— We analyzed the prominence. When this magnetoplasma structure lost stability and was thrown into space, an opportunity arose to study the heat exchange processes inside it, one of the authors of the discovery, ISTP chief researcher Arkady Uralov told Izvestia.
He explained that this phenomenon is otherwise called a coronal mass ejection.
Today, the Siberian radioheliograph is the only instrument on the planet that makes it possible to study such events in good quality in the microwave range.
Why does a “ball” of plasma expand in space?
In particular, thanks to the new instrument, scientists tracked the prominence until it moved away from the star to a distance of one of its radii. That is about 700 thousand km. During this time, the volume of mass ejected from the solar corona increased hundreds of times.
“The discovery is that we discovered the release of thermal energy inside the expanding “ball” and established the main cause of this phenomenon – the electric currents that flow inside the plasma. A similar phenomenon occurs when wires are heated. Then we can simply assume that the remaining parts of the solar corona are heated in a similar way,” explained Arkady Uralov.
He noted that in the prominence the density of matter is higher, currents and magnetic lines are stronger. Therefore, using the example of this event, scientists were able to see the nature of the phenomenon as a whole.
“From a practical point of view, the study is significant because prominences are rather unstable structures. Sooner or later they are destroyed, and a large amount of solar plasma is concentrated in them. If part of this substance heads towards the Earth and interacts with the planet’s magnetic field, this can provoke magnetic storms, Sergei Kuzin, head of the Solar Astronomy Laboratory at the Space Research Institute of the Russian Academy of Sciences, told Izvestia.
The expert added that any data about the Sun is useful, since fundamental processes on our planet directly depend on the activity of the star. For example, such as global warming, the formation of ocean currents and the development of organic matter.
“It is important that the researchers showed how one of the processes that heats the plasma in the corona (that is, in the vicinity of the Sun) also has an effect at large distances from the sun. It prevents the substance of the prominence from cooling quickly, and the speed of the particles depends on this. They, in turn, can affect the operation of artificial satellites in orbit or electronics and electrical equipment on Earth,” explained a professor at the Institute of Laser and Plasma Technologies of the National Research Nuclear University MEPhI Vladimir Reshetov.
In his opinion, the Siberian radioheliograph will bring many more interesting discoveries, because the behavior of the Sun, its structure, magnetic lines, black spots on its surface are phenomena that scientists still do not understand enough. At the same time, the findings will be predictive in nature, since the echoes of solar storms are always reflected on our planet.
Another important aspect of the research was the development of a technique for measuring the temperature and concentration of an expanding plasma using its microwave radiation, the expert added.
At the moment, domestic heliophysics lags behind the world’s advanced models in terms of equipment, summed up astronomer and professor at Irkutsk State University Sergei Yazev. At the same time, he noted that the problem is now partially solved through the construction of the National Heliophysical Center of the Russian Academy of Sciences on the basis of ISTP. According to him, within the framework of this project, mega-installations are being commissioned that will allow Russian scientists to study the Sun and other space objects at a qualitatively new level.