American scientists, based on data from NASA’s Parker Solar Probe, measured the intensity of the electron flow — the main component of the solar wind, which for the first time made it possible to accurately calculate the potential of the Sun’s electric field. The results of the study are published in The Astrophysical Journal.
The electric field of the Sun arises as a result of the interaction of protons and electrons formed during the separation of hydrogen atoms under the action of heat generated by thermonuclear fusion deep inside the Sun. Both these and other particles make up the solar wind, carried away from the solar surface in the direction of the outer layer of the heliosphere.
Some electrons are held in the flow by positively charged protons, and some, having a mass of 1800 times less than that of protons, break away from them and return back to the surface of the Sun. This movement of electrons determines the electric field of the Sun.
Physicists from the University of Iowa analyzed new data obtained from the Parker Solar Probe automatic spacecraft for studying the Sun’s corona, which flew just 0.1 astronomical units from the star – closer than any ship before — and got a new idea of the Sun’s electric field.
“The key point is that you can’t make such measurements away from the Sun. You can make them only when you get closer — -the words of one of the authors of the study, Jasper Halekas, associate professor of the Department of Physics and Astronomy, are quoted in a press release of the university. — It’s like trying to understand a waterfall by looking at a river a mile downstream. The measurements that we made at a distance of 0.1 astronomical units are like inside a waterfall.”
In particular, the researchers estimated the ratio of departing and returning electrons and calculated the parameters of the Sun’s electric field, its width and configuration more accurately than ever before.
“The electrons are trying to escape, and the protons are trying to pull them back. This is the electric field,” Halekas says. — If there was no electric field, all the electrons would rush away and disappear. But the electric field holds all the particles together as one homogeneous flow.”
Researchers figuratively describe the electric field of the Sun in the form of a huge bowl, and electrons-in the form of balls rolling along its inner surface at different speeds. Some electrons, or balls, are mobile enough to cross the edge of the bowl, while others gradually slow down and eventually roll to the bottom of the bowl.
“In fact, there is an energy boundary between those balls that leave the bowl and those that can’t do it, and it can be measured. Being close enough to the Sun, we can make accurate measurements of the distribution of electrons. First of all, we measure those electrons that return, and not those that fly away,” the scientist explains. — So we can determine how much of this acceleration is provided by the electric field of the Sun. It looks like this is a very small part. This is not the main thing that gives momentum to the solar wind, but it indicates other mechanisms that give more energy.”
The authors hope that the results of their research will allow us to get a more accurate idea of the solar wind — a jet of plasma that flies away from the Sun at a speed of millions of kilometers per hour and washes the Earth and other planets of the Solar System, and also has a significant impact on the operation of comic devices.
