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Space Weather

Mapping solar wind to its source on the Sun

Space weather forecasting requires knowing where solar wind originated on the Sun. By combining helium abundance and cross helicity measurements, we can classify solar wind into distinct source-region types and predict its impact on Earth's magnetosphere.

This schematic diagram divides the solar wind into regions based on wave activity (horizontal axis) and helium content (vertical axis), with speed shown by contour lines.

Three-parameter map classifies solar wind by origin

This schematic diagram divides the solar wind into regions based on wave activity (horizontal axis) and helium content (vertical axis), with speed shown by contour lines. A green region at the bottom marks wind from intermittently open sources. A red region at upper right marks wind from continuously open sources. An orange region in the middle represents wind of ambiguous origin. A small red region at upper left highlights helium-rich but wave-poor wind that the companion paper hypothesizes comes from transient events. An arrow labeled 'More Open' points toward the continuously open region.
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Related Figures

This contour plot maps the average hydrogen density fluctuation level using color across solar wind speed (horizontal axis) and wave activity (vertical axis).

Compressibility and wave activity are inversely related

Compressibility and wave activity are inversely related across the speed-wave activity plane.

Shows how helium abundance varies with cross helicity in different solar wind classification regimes

This contour plot shows the average wave activity level (color) as a function of solar wind speed (horizontal axis) and helium abundance (vertical axis).

Wave activity maps onto the helium-speed plane

The saturation points consistently fall in the region of moderately high wave activity, above the 0.6 contour.

Demonstrates the universal scaling behavior that underlies the classification scheme

See Also

Helium Abundance

Helium abundance is a key parameter in the classification scheme

Solar Wind Acceleration

Cross helicity (Alfvénicity) is the other key parameter in the classification

Solar Wind Compressibility

Compressibility refines the classification boundaries

Sources Of The Solar Wind

The classification scheme maps solar wind back to its coronal source regions

Source

On the Regulation of the Solar Wind Helium Abundance by the Hydrogen Compressibility

The Astrophysical Journal Letters (2026)

View Paper

© 2026 The Author(s). Published by the American Astronomical Society. CC BY 4.0