A new study led by the University of Hawai’i (UH) at Mānoa has helped
refine understanding of the amount of hydrogen, helium and other elements
present in violent outbursts from the Sun, and other types of solar “wind,” a
stream of ionized atoms ejected from the Sun.
Coronal mass
ejections (CME) are giant plasma bursts that erupt from the sun, heading out
into the solar system at speeds as fast as 2 million miles per hour. Like the
sun itself, the majority of a CME’s atoms are hydrogen. When these particles
interact with Earth’s atmosphere, they lead to the brilliant multicolored
lights of the Aurora Borealis. They also have the potential to knock out
communications, bringing modern civilization to a standstill.
And their cause
is pretty much a mystery.
UH Manoa School
of Ocean and Earth Science and Technology (SOEST) researcher Gary Huss led a
team of scientists in investigating a sample of solar wind collected by NASA’s
Genesis mission.
Most of our
understanding of the composition of the sun, which makes up 99.8% of the mass
of the Solar System, has come from astronomical observations and measurements
of a rare type of meteorite. In 2001, the Genesis probe headed to space to
gather samples of solar wind in pure materials, and bring the material back to
Earth to be studied in a lab. Those samples represented particles gathered from
different sources of solar wind, including those thrown off by CMEs.
The Genesis
samples allowed for a more accurate assessment of the hydrogen abundance in
CMEs and other components of the solar wind. About 91% of the Sun’s atoms are
hydrogen, so everything that happens in the solar wind plasma is influenced by
hydrogen.
However,
measuring hydrogen in the Genesis samples proved to be a challenge. An
important component of the recent work was to develop appropriate standards
using terrestrial minerals with known amounts of hydrogen, implanted with
hydrogen by a laboratory accelerator.
A precise
determination of the amount of hydrogen in the solar wind allowed researchers
to discern small differences in the amount of neon and helium relative to
hydrogen ejected by these massive solar ejections. Helium and neon, both noble
gases, are difficult to ionize. The new measurements of hydrogen showed that
helium and neon were both enriched in coronal mass ejections, providing clues
to the underlying physics in the Sun that causes the coronal mass ejections.
In the very
energetic event, “the ejected material appears to be enriched almost
systematically in atoms that require the most energy to ionize,” said Ryan
Ogliore, co-author and assistant professor of physics at Washington University
in St. Louis. “That tells us a lot about the physics involved in the first
stages of the explosion on the Sun.”
This finding
brings researchers one step closer to understanding the origins of these
particular solar events.
Journal article: https://onlinelibrary.wiley.com/doi/abs/10.1111/maps.13420
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