The Effects of Non-Equilibrium Features on Solar Wind Plasma Evolution

Abstract:

The small-scale behaviors of microinstabilities in solar wind plasma are important to understanding larger scale energy transfer and dissipation in the solar wind. While typical treatments of plasma waves assume a hot, drifting bi-Maxwellian distribution function, distribution functions observed in the solar wind often contain significant departures from this idealized model. This project investigates how these deviations from an idealized bi-Maxwellian distribution function affect the onset and evolution of microinstabilities in the solar wind. To this end, we use the Arbitrary Linear Plasma Solver (ALPS) to find the normal mode frequencies and growth rates of the expected waves using actual solar wind proton distributions measured by the Wind spacecraft which are then compared to the results from a bi-Maxwellian fit of the same proton distributions. By doing this, we can quantify how important these non-equilibrium features are to the evolution of the plasma. We plan to apply this analysis to non-Maxwellian proton distributions observed by Parker Solar Probe to gain insight into the different plasmas observed closer to the Sun and how the solar wind evolves as it moves out from the Sun.