Constraining Solar Wind Heating Processes by Kinetic Properties of Heavy Ions

Area of Science:

• Space Physics
• Plasma Physics
• Solar Physics

Background:

• The solar wind is a stream of charged particles released from the upper atmosphere of the Sun.
• Understanding the composition and thermodynamics of the solar wind is crucial for space weather prediction.
• Heavy ions in the solar wind provide insights into coronal conditions and plasma processes.

Purpose of the Study:

• To analyze the temperature-mass dependence of heavy ions in collisionally young solar wind plasma.
• To compare observational data with theoretical models of ion heating and transport.
• To provide new constraints for models of multispecies plasma heating.

Main Methods:

• Analysis of heavy ion components (A>4 amu) in solar wind plasma.
• Fitting observational data to linear and power-law models for temperature-mass dependence.
• Comparison of observed ion heating with predictions from turbulent transport and kinetic dissipation models.

Main Results:

• A clear, stable linear dependence of ion temperature on mass was observed: Tᵢ/Tₚ=(1.35±.02)mᵢ/mₚ.
• This linear fit described the data twice as well as the best-fit power law.
• Models agreed with observations for intermediate collisional age plasma (m/q<3.5) but not for the youngest plasma.

Conclusions:

• The observed temperature-mass dependence reflects conditions in the solar corona.
• Current models of turbulent transport and kinetic dissipation require refinement to explain heating in the earliest solar wind.
• These findings offer testable predictions for future missions like Solar Probe Plus and Solar Orbiter.