Particle physics research

New research could help scientists uncover the physics of solar wind

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 corona. solar. 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 article is published in Astrophysical Journal Letters, a scientific journal of the American Astronomical Society (AAS) that publishes high-impact astrophysical research.

Scientists used data collected by the Parker Solar Probe, launched in 2018 to help 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 had an impact not only on understanding the solar wind and the winds of other stars, but also on understanding the heat flow of many other astrophysical systems to which we cannot send satellites, 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.

In addition to Cattell, the research team included Elizabeth Hanson, John Dombeck, research director Keith Goetz and Ph.D., from the School of Physics and Astronomy at the University of Minnesota. alumnus Mike Johnson; Aaron Breneman, researcher at NASA’s Goddard Space Flight Center; Jasper Halekas, associate professor at the University of Iowa; Stuart Bale, professor at the University of California at Berkeley (UCB), Marc Pulupa, associate researcher at the UCB Space Science Laboratory, David Larson, project scientist, and Phyllis Whittlesey, assistant researcher; University of Orleans, France Professor Thierry Dudok de Wit; Katherine Goodrich, assistant professor at West Virginia University; University of Colorado, Boulder Assistant Professor David Malaspina; Smithsonian Astrophysical Observatory researchers Tony Case and Michael Stevens; and Professor Justin C. Kasper of the University of Michigan.

The research was funded by NASA and the simulation work was supported by the Minnesota Supercomputing Institute on the University of Minnesota Twin Cities campus. Parker Solar Probe is part of NASA’s Living with a Star program to explore aspects of the Sun-Earth system that directly affect life and society. The program is managed by NASA’s Goddard Space Flight Center for the Heliophysics Division of NASA’s Science Mission Directorate. Johns Hopkins Applied Physics Laboratory in Laurel, Maryland built and operates the Parker Solar Probe spacecraft and manages the mission for NASA.

Read the full paper, titled “Parker Solar Probe, Evidence for No Near-Sun Whistlers to Scatter Strahl and Regulate Heat Flux,” on the Astrophysical Journal Letters website.