Newly Discovered Particles in Solar Wind May Force Rethink of Space Weather Models
WASHINGTON – A new study utilizingโฃ data from NASA’sโ Magnetospheric โขMultiscale (MMS) mission suggests that previously underestimated particles in the solar wind – known as Pick-Up Ions (PUIs) – โขmay be generating waves thatโค substantially โฃimpact the heating โฃand behavior of the space habitat around Earth. The findings, โขpublished May 25, 2024, in the Journal of Geophysical Research: Spaceโข physics, could necessitate updates โto โcurrent models of the solar wind and its influence throughout the heliosphere.
Launched in 2015, the MMS mission deployedโ four spacecraftโข to investigate Earth’s magnetosphere, the protective magnetic โขbubble shielding theโ planet from harmful solar and โcosmic radiation.Researchers, led by Michael J. Starkey, analyzed โฃMMS magnetic field measurements โand found evidence of wave activityโ correlatedโ with the presence of PUIs.
PUIs are formed when neutral particlesโ traveling through the heliosphere become โฃionized by the solar wind, thenโข spiral around โคthe local magnetic field, creating a plasma population distinct from standard solarโ wind particles. The study revealed a characteristic velocity distribution of thes PUIs, observed โคwithout other notable โenergetic ion or electron populations.
“The results of this study indicate that PUIs can in factโ generateโค waves in โคthe solarโ wind near earth and motivate the need for โfurtherโค statistical studies of these processes,” Starkey said. “It might potentiallyโค be that PUIs play a largerโข role in the heating and thermalization of the solar wind near Earth than previously thought, which would โhave largeโข implications for modelsโ of the solar โwind throughout the heliosphere.”
While the research team persistentโ theโ waves where likely generated by helium and/or hydrogen PUIs,instrument limitations preventedโฃ them โขfrom identifying the precise ion species responsible. They โmodeled โthe individual ion components – solarโ wind and PUIs – to pinpoint potential wave generators.
The โimplications of this revelation extend beyond Earth’s immediate vicinity. โas distance from the Sun increases, the density of PUIs in the solar wind alsoโฃ rises,โฃ possibly increasing their contribution to wave-particleโ interactions and the โoverall heating of the solar wind. โ โAt the outer edges of the solar system, PUIs already contribute significantly โto the total dynamic pressure in the solar wind, impacting processes at the termination shock andโค in the heliosheath.
“Near Earth, the intensity of PUIs โฃis relatively low, and so it is typically assumed that their โฃcontribution to wave-particle interactions in the solarโ windโ is negligible,” โคStarkey added.”If this assumption is false, current theory andโ modeling โคof the solar windโ and โits evolution throughout the heliosphere โขwouldโ need to be updated.”
The study, โtitled “First MMS Observations of Waves Possibly โGenerated by PUIs Near Earth,” is available with DOI: 10.1029/2024JA033660.