New research could help scientists unravel the physics of solar wind
(News from Nanowerk) A new study by researchers at the University of Minnesota Twin Cities, using data from NASA’s Parker Solar Probe, provides insight into what generates and accelerates the solar wind, a stream of charged particles released from the solar corona.
Understanding how the solar wind works can help scientists predict “space weather,” or the response to solar activity, such as solar flares, that can impact both astronauts in space and a much of the technology that people on Earth depend on.
The paper is published in Astrophysical Journal Letters (“Parker Solar Probe proves the absence of whistlers near the Sun to disperse strahl and regulate heat flux”).
The scientists used data collected by Parker Solar Probe, which was launched in 2018 with the aim of helping scientists understand what heats the solar corona (the sun’s outer atmosphere) and generates the solar wind. To answer these questions, scientists need to understand how energy flows from the sun. The latest set of data was obtained in August 2021 at a distance of 4.8 million kilometers from the sun – the closest a spacecraft has ever been to the star.
Previous research has indicated that in the solar wind, at distances of about 35 solar radii (a solar radius is just over 432,000 miles) to Earth’s orbit at about 215 solar radii, electromagnetic waves called “Whistling” waves help regulate heat flow, a form of energy flow. In this new study, the University of Minnesota-led research team found that in a region closer to the sun, within about 28 solar radii, there are no whistling waves.
Instead, the researchers saw another type of wave that was electrostatic instead of electromagnetic. And in that same region, they noticed something else: the electrons showed the effect of an electric field created in part by the pull of solar gravity, similar to what happens at the Earth’s poles where a ” polar wind” is accelerated.
“What we found is that when we enter 28 solar radii, we lose the whistlers. This means the whistlers can’t do anything to control the heat flow in that region,” said Cynthia Cattell, author principal of the paper and a professor in the School of Physics and Astronomy at the University of Minnesota Twin Cities.” This result was very, very surprising to people. It has impacts not only for understanding the solar wind and the winds of other stars, but it is also important for understanding the heat flow of many other astrophysical systems that we cannot send satellites to, such as the formation of star systems.
Knowing more about the solar wind is also important to scientists for other reasons. For one thing, it can disrupt the Earth’s magnetic field, generating “space weather” events that can cause satellites to malfunction, affect communications and GPS signals, and cause power outages on Earth at northern latitudes like Minnesota. . Energetic particles that travel through the solar wind can also be harmful to astronauts traveling in space.
“Scientists want to be able to predict space weather,” Cattell explained. “And if you don’t understand the details of the energy flow near the sun, you can’t predict how fast the solar wind will travel or what its density will be when it hits Earth. These are some of the properties that determine how solar activity affects us.
By the end of 2024, the Parker Solar Probe will fly an even closer 3.8 million miles from the sun. Going forward, Cattell and his colleagues are excited to see the next set of data from the spacecraft. Their next goal will be to understand why this absence of whistling waves exists so close to the sun, how electrons accelerated by the electric field associated with gravity could excite other waves, and how this affects the solar wind.