Reconciling Spectroscopic Electron Temperature Measurements in the Solar Corona with In Situ Charge State...

Area of Science:

• Solar physics
• Plasma physics
• Astrophysics

Background:

• Spectroscopic measurements in the inner corona suggest electron temperatures inconsistent with observed solar wind ion fractions.
• This discrepancy has been a long-standing puzzle in solar and space physics.

Purpose of the Study:

• To reconcile the conflicting measurements of electron temperatures and ion fractions between the inner corona and the solar wind.
• To identify the necessary conditions in the inner corona that explain the observed solar wind composition.

Main Methods:

• Investigated the role of electron distribution functions and ion flow speeds in the inner corona.
• Developed theoretical models to demonstrate the conditions required for reconciliation.
• Analyzed two specific examples to illustrate the general requirements.

Main Results:

• Reconciliation requires a Maxwellian electron distribution at the coronal base that rapidly becomes non-Maxwellian with height.
• Differential ion flow speeds are crucial for separating "freezing-in" distances and exposing ions to different electron distributions.
• The specific details of these distributions are sensitive to temperature, density, and flow profiles.

Conclusions:

• The observed solar wind ion fractions can be explained by specific conditions in the inner corona, including evolving electron distribution functions and differential ion flows.
• These findings provide a framework for understanding the formation of solar wind plasma composition.
• Further detailed modeling is needed to capture the precise plasma conditions responsible for ion fractionation.