Ion-driven Instabilities in the Inner Heliosphere. I. Statistical Trends

  title={Ion-driven Instabilities in the Inner Heliosphere. I. Statistical Trends},
  author={Mihailo M. Martinovi{\'c} and Kristopher Gregory Klein and Tereza Ďurovcov{\'a} and Benjamin L. Alterman},
  journal={The Astrophysical Journal},
Instabilities described by linear theory characterize an important form of wave–particle interaction in the solar wind. We diagnose unstable behavior of solar wind plasma between 0.3 and 1 au via the Nyquist criterion, applying it to fits of ∼1.5M proton and α particle Velocity Distribution Functions (VDFs) observed by Helios I and II. The variation of the fraction of unstable intervals with radial distance from the Sun is linear, signaling a gradual decline in the activity of unstable modes… 


Linear Stability in the Inner Heliosphere: Helios Re-evaluated
Wave-particle instabilities driven by departures from local thermodynamic equilibrium have been conjectured to play a role in governing solar wind dynamics. We calculate the statistical variation of
Signatures of kinetic instabilities in the solar wind
[1] An analysis of ion non-thermal properties in the fast solar wind based on Ulysses data is reported. The radial evolution of the main proton moments (density, temperature, and drift velocities)
Kinetic instabilities in the solar wind driven by temperature anisotropies
The present paper comprises a review of kinetic instabilities that may be operative in the solar wind, and how they influence the dynamics thereof. The review is limited to collective plasma
Alpha particle thermodynamics in the inner heliosphere fast solar wind
Context. Plasma processes occurring in the corona and solar wind can be probed by studying the thermodynamic properties of different ion species. However, most in situ observations of positive ions
Predicted Impacts of Proton Temperature Anisotropy on Solar Wind Turbulence
Particle velocity distributions measured in the weakly collisional solar wind are frequently found to be non-Maxwellian, but how these non-Maxwellian distributions impact the physics of plasma
Thermodynamics of pure fast solar wind: radial evolution of the temperature–speed relationship in the inner heliosphere
A strong correlation between speed and proton temperature has been observed, across many years, on hourly averaged measurements in the solar wind. Here, we show that this relationship is also
Parker Solar Probe Observations of Proton Beams Simultaneous with Ion-scale Waves
Parker Solar Probe (PSP), NASA's latest and closest mission to the Sun, is on a journey to investigate fundamental enigmas of the inner heliosphere. This paper reports initial observations made by
Evolution of Relative Drifts in the Expanding Solar Wind: Helios Observations
Ion velocity distribution functions (VDFs) measured in-situ in the solar wind show often large deviations from a simple Maxwellian distribution. Even a main part of the proton VDF (proton core)
The multi-scale nature of the solar wind
The role of expansion effects, non-equilibrium distribution functions, collisions, waves, turbulence, and kinetic microinstabilities for the multi-scale plasma evolution are discussed.
Evidence for electron Landau damping in space plasma turbulence
A field-particle correlation technique is presented to directly measure the transfer of energy between the turbulent electromagnetic field and electrons in the Earth’s magnetosheath, the region of solar wind downstream of the Earth's bow shock, and shows a signature consistent with Landau damping.