NASA’s Parker Solar Probe and ESA’s Solar Orbiter missions measure the same plasma flow from the Sun at different distances. Parker measured many magnetic waves near the edge of the corona (the “Alfvén surface”), while Solar Orbiter, located beyond Venus’ orbit, observed that the waves had disappeared and their energy had been used to heat and accelerate the plasma. Credit: Yeimy Rivera and Samuel Badman. The solar image data comes from NASA’s Solar Dynamics Observatory. The images were created with the open-source Python software SunPy (
By studying data from NASA’s Parker Solar Probe and ESA’s Solar Orbiter, an international team of astrophysicists has discovered that Alfvén waves cause the solar wind to accelerate and heat up.
In their study, published in the journal ScienceThe group compared data from the two space probes to learn more about the energy sources impacting the solar wind.
Luca Sorriso-Valvo and Francesco Malara, respectively from the CNR–Institute of Plasma Science and Technology, Sweden, and the University of Calabria, Italy, published a Perspective article in the same issue of the journal describing the work carried out by the group.
Previous research has shown that as the solar wind moves out from the solar corona, it cools, but it also speeds up. Previous research has also shown that the cooling doesn’t happen as quickly as it should because of free expansion, a finding that suggests an additional heat source. Some researchers have suggested that the heat source likely comes from Alfvén waves, a type of electromagnetic plasma wave. In this new study, the researchers found evidence to support that theory.
To find out whether Alfvén waves are responsible for the acceleration and heat contribution to the solar wind, the research team compared data from NASA’s Parker Solar Probe and ESA’s Solar Orbiter at a convenient moment of alignment during their voyages.
During this period, the solar wind hit the second probe 40 hours after the first, allowing the researchers to measure the energy differences. They found large-amplitude Alfvén waves pushing the solar wind, forcing a change in direction. Measurements from the second probe showed no evidence of such a force. They also showed that the solar wind had warmed.
By calculating the amount of energy lost by the Alfvén waves, the researchers found that it corresponded to the energy needed to heat the solar wind and accelerate it in a way that matched the observations of the second probe.
The research team suggests that their observations and calculations present a strong argument for Alfvén waves as the driver of solar wind acceleration and heating.
More information:
Yeimy J. Rivera et al., In situ observations of large amplitude Alfvén waves heating and accelerating the solar wind, Science (2024). DOI: 10.1126/science.adk6953
Luca Sorriso-Valvo et al, Interplanetary Rendezvous in a Solar Wind Stream, Science (2024). DOI: 10.1126/science.adr5854
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Quote:Space probe data show Alfvén waves cause solar wind to accelerate and warm (2024, August 31) retrieved September 2, 2024 from
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