Inferred Linear Stability of Parker Solar Probe Observations using One- and Two-Component Proton Distributions

Abstract

The hot and diffuse nature of the Sun's extended atmosphere allows it to persist in non-equilibrium states for long enough that wave-particle instabilities can arise and modify the evolution of the expanding solar wind. Determining which instabilities arise, and how significant a role they play in governing the dynamics of the solar wind, has been a decades-long process involving in situ observations at a variety of radial distances. With new measurements from Parker Solar Probe (PSP), we can study what wave modes are driven near the Sun, and calculate what instabilities are predicted for different models of the underlying particle populations. We model two hours-long intervals of PSP/SPAN-i measurements of the proton phase-space density during PSP's fourth perihelion with the Sun using two commonly used descriptions for the underlying velocity distribution. The linear stability and growth rates associated with the two models are calculated and compared. We find that both selected intervals are susceptible to resonant instabilities, though the growth rates and kind of modes driven unstable vary depending on if the protons are modeled using one or two components. In some cases, the predicted growth rates are large enough to compete with other dynamic processes, such as the nonlinear turbulent transfer of energy, in contrast with relatively slower instabilities at larger radial distances from the Sun.

arXiv comment10 pages, 9 figures, accepted in ApJ

References in corpus (14)

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Cited by in corpus (21)

• Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum
• The In Situ Signature of Cyclotron Resonant Heating
• Strong perpendicular velocity-space in proton beams observed by Parker Solar Probe
• Patches of magnetic switchbacks and their origins
• The Radial Distribution of Ion-scale Waves in the Inner Heliosphere
• Modeling ion beams, kinetic instabilities, and waves observed by the Parker Solar Probe near perihelia
• Ion-Driven Instabilities in the Inner Heliosphere I: Statistical Trends
• Magnetic reconnection as a mechanism to produce multiple protonpopulations and beams locally in the solar wind
• Electromagnetic Proton Beam Instabilities in the Inner Heliosphere: Energy Transfer Rate, Radial Distribution, and Effective Excitation
• Cross Helicity and the Helium Abundance as an in situ Metric of Solar Wind Acceleration
• Fully Kinetic Simulations of Proton-Beam-Driven Instabilities from Parker Solar Probe Observations
• Ion-Driven Instabilities in the Inner Heliosphere II: Classification and Multi-Dimensional Mapping
• Modeling hot, anisotropic ion beams in the solar wind motivated by the Parker Solar Probe observations near perihelia
• Growth of Outward Propagating Fast-Magnetosonic/Whistler Waves in the Inner Heliosphere Observed by Parker Solar Probe
• Decoding the formation of hammerhead ion populations observed by Parker Solar Probe
• The Evolution of Heavy Ion Abundances with Solar Activity
• Formation of Magnetic Switchbacks via expanding Alfvén Waves
• Characterizing the Impact of Alfvén Wave Forcing in Interplanetary Space on the Distribution of near-Earth Solar Wind Speeds
• Evolution of an Alfvén Wave-Driven Proton Beam in the Expanding Solar Wind
• On the Regulation of the Solar Wind Helium Abundance by the Hydrogen Compressibility
• Hybrid simulations of the proton beam instabilities in the young solar wind. The formation of hammerhead-like distributions