Monday, October 19, 2026 at 3:30 pm

JILA auditorium

Ben Alterman, Goddard Space Flight Center

"Using 30 Years of Solar Wind Helium Abundance Observations to Derive Insights about the Sun as a Star"

Abstract:

The solar wind helium abundance (A_He=100×n_He/n_H) tracks solar activity. The correlation f A_He with sunspot number (SSN, the conventional solar cycle clock) is stronger in slow wind than fast wind. The difference in the strength of these correlation coefficients is likely a result of how the differences ins low and fast wind sources evolve with solar activity. In this talk, I will outline results connecting fast and slow wind to distinct sources on the Sun and how the physical mechanisms that drive the release of helium into the solar wind differ between these regions. I will then present new results showing that: The evolution of A_He with solar activity is indistinguishable when characterized as a function of SSN or the open magnetic flux from active regions (ARs); Slow wind A_He is a solar activity indicator with fixed amplitude that does not display the asymmetry characterized by the Waldmeier effect; and A_He in slow solar wind and interplanetary coronal mass ejections (ICMEs) are likely from the same solar wind source region and may therefore be released into interplanetary space by similar mechanisms. Through this talk, I will thread the following themes. The closed loops characteristic of slow wind sources are likely a key driver of the difference between slow and fast wind A_He. 30+ years of A_He observations from a single, stable instrument are essential for characterizing these long-term trends. Because gravitational settling is generally characteristic of closed loops, these results may provide insight into stars beyond our Sun.

Back to Speakers