Wednesday, January 22, 2025 - 3:10 p.m. to 4:10 p.m.
Morse Hall, rm 301 -OR- Zoom
Speaker:
Dr. Benjamin Alterman – NASA Goddard Space Flight Center
Abstract:
Using solar wind observations of the helium abundance from the Wind spacecraft and heavy ion abundances from the Advanced Composition Explorer (ACE) along with observations of the Sunspot Number – a long-studied proxy for the Sun’s activity – we will discuss the imprint of different solar wind source regions on observations collected at 1 AU. We will draw inferences about the role of helium in the acceleration of coronal plasma into the solar wind. Using the Alfvénicity – a metric related to the solar wind acceleration that occurs during transit through interplanetary space – we will derive a solar wind classification scheme for near-Earth observations that is related to the differences in the source regions from which it emanates.
Doubly ionized helium is the 2nd most abundant element in the solar wind. The solar wind’s properties are a function of the source region from which it emanates on the Sun. This includes the abundances of solar wind Helium and rarer, heavier elements. The speed of the solar wind, when observed near Earth, is also related to the type of source region from which the solar wind originated.
Early solar wind models are unable to explain how the solar wind achieved the asymptotically fastest, non-transient speeds observed at 1 AU and the solar wind must be accelerated during transit through interplanetary space. Only recently have observations identified the different mechanisms responsible for accelerating solar wind from different source regions during its propagation through interplanetary space. However, the solar wind speed is also known to be an insufficient for identifying the type of solar source from which it originated, likely because these different acceleration mechanisms accelerate the solar wind into different speed regimes that overlap. Furthermore, the mechanism that provides the coronal plasma sufficient energy to accelerate into the solar wind is still undetermined. These mysteries are further complicated by the Sun’s evolution through its 11-year activity cycle and the impact of the solar cycle on in situ observations.
Free drinks and refreshments will be provided in Morse Hall.
Schedule:
Check out the rest of this season's Space Science Seminar Series, as well as previous recordings.
