Solar wind thermally induced magnetic fluctuations

Area of Science:

• Plasma Physics
• Space Physics
• Astrophysics

Background:

• Solar wind magnetic fluctuations are crucial for understanding space weather and plasma dynamics.
• Previous studies often focused on wave excitations or instability thresholds.
• Anisotropic electron-proton plasmas are common in space environments like the solar wind.

Purpose of the Study:

• To provide a kinetic description of Alfvén-cyclotron magnetic fluctuations in anisotropic electron-proton plasmas.
• To investigate the contribution of spontaneous fluctuations to observed solar wind magnetic fluctuations.
• To compare analytical results with existing observational and simulation data.

Main Methods:

• Analytical treatment using the fluctuation-dissipation theorem.
• Kinetic description of Alfvén-cyclotron waves.
• Comparison with observational data from solar wind missions (e.g., Bale et al., 2009).
• Validation against results from hybrid plasma simulations.

Main Results:

• Spontaneous fluctuations in stable plasma distributions significantly contribute to magnetic fluctuations.
• This contribution is evident even far below instability thresholds.
• The analytical results are consistent with hybrid simulations.
• No adjustable parameters or wave excitations were required for the model.

Conclusions:

• The fluctuation-dissipation theorem provides a consistent explanation for observed solar wind magnetic fluctuations.
• Spontaneous fluctuations play a vital role in the energy cascade and dynamics of solar wind plasma.
• This work advances the understanding of fundamental plasma processes in astrophysical environments.