# LIMITS ON ALPHA PARTICLE TEMPERATURE ANISOTROPY AND DIFFERENTIAL FLOW FROM KINETIC INSTABILITIES: SOLAR WIND OBSERVATIONS

@article{Bourouaine2013LIMITSOA,
title={LIMITS ON ALPHA PARTICLE TEMPERATURE ANISOTROPY AND DIFFERENTIAL FLOW FROM KINETIC INSTABILITIES: SOLAR WIND OBSERVATIONS},
author={Sofiane Bourouaine and Daniel Verscharen and Benjamin D. G. Chandran and Bennett A. Maruca and Justin C. Kasper},
journal={The Astrophysical Journal},
year={2013},
volume={777}
}
• Published 16 September 2013
• Physics
• The Astrophysical Journal
Previous studies have shown that the observed temperature anisotropies of protons and alpha particles in the solar wind are constrained by theoretical thresholds for pressure and anisotropy driven instabilities such as the Alfven/ion-cyclotron (A/IC) and fast-magnetosonic/whistler (FM/W) instabilities. In this Letter, we use a long period of in situ measurements provided by the Wind spacecraft's Faraday cups to investigate the combined constraint on the alpha proton differential flow velocity…
43 Citations

## Figures from this paper

Effects of alpha-proton drift velocity on alpha particle firehose instability
• Physics
• 2016
In situ measurements have shown that the less-abundant alpha particles are characterized by temperature anisotropy which could drive the anisotropy-driven kinetic instabilities in the solar wind. In
Fire Hose instability driven by alpha particle temperature anisotropy
• Physics
• 2015
We investigate properties of a solar wind-like plasma including a secondary alpha particle population exhibiting a parallel temperature anisotropy with respect to the background magnetic field, using
ENSEMBLE SIMULATIONS OF PROTON HEATING IN THE SOLAR WIND VIA TURBULENCE AND ION CYCLOTRON RESONANCE
Protons in the solar corona and heliosphere exhibit anisotropic velocity distributions, violation of magnetic moment conservation, and a general lack of thermal equilibrium with the other particle
Nonlinear Evolution of Ion Kinetic Instabilities in the Solar Wind
In-situ observations of the solar wind (SW) plasma from 0.29 to 1 AU show that the protons and α$\alpha$ particles are often non-Maxwellian, with evidence of kinetic instabilities, temperature
Parallel-propagating Fluctuations at Proton-kinetic Scales in the Solar Wind Are Dominated By Kinetic Instabilities
• Physics
The Astrophysical Journal
• 2019
We use magnetic helicity to characterise solar wind fluctuations at proton-kinetic scales from Wind observations. For the first time, we separate the contributions to helicity from fluctuations
Interplay of Electron and Proton Instabilities in Expanding Solar Wind
• Physics
• 2017
Protons and electrons observed in the solar wind possess temperature anisotropies for which  upper and lower bounds appear to be partially regulated by marginal conditions associated with various
A PARALLEL-PROPAGATING ALFVÉNIC ION-BEAM INSTABILITY IN THE HIGH-BETA SOLAR WIND
• Physics
• 2013
We investigate the conditions under which parallel-propagating Alfv?n/ion-cyclotron waves are driven unstable by an isotropic (T ?? = T ??) population of alpha particles drifting parallel to the
SOLAR WIND PROTONS AT 1 AU: TRENDS AND BOUNDS, CONSTRAINTS AND CORRELATIONS
• Physics, Geology
• 2014
The proton temperature anisotropy in the solar wind exhibits apparent bounds which are compatible with the theoretical constraints imposed by temperature-anisotropy-driven kinetic instabilities.
DISSIPATION OF PARALLEL AND OBLIQUE ALFVEN-CYCLOTRON WAVES-IMPLICATIONS FOR HEATING OF ALPHA PARTICLES IN THE SOLAR WIND
• Physics
• 2015
We perform 2.5D hybrid simulations with massless fluid electrons and kinetic particle-in-cell ions to study the temporal evolution of ion temperatures, temperature anisotropies, and velocity
Relative drifts and temperature anisotropies of protons and α particles in the expanding solar wind: 2.5D hybrid simulations
• Physics
• 2015
Context. We perform 2.5D hybrid simulations to investigate the origin and evolution of relative drift speeds between protons and α particles in the collisionless turbulent low- ˜ β solar wind plasma.

## References

SHOWING 1-10 OF 30 REFERENCES
INSTABILITIES DRIVEN BY THE DRIFT AND TEMPERATURE ANISOTROPY OF ALPHA PARTICLES IN THE SOLAR WIND
• Physics
• 2013
We investigate the conditions under which parallel-propagating Alfven/ion-cyclotron (A/IC) waves and fast-magnetosonic/whistler (FM/W) waves are driven unstable by the differential flow and
INSTABILITY-DRIVEN LIMITS ON HELIUM TEMPERATURE ANISOTROPY IN THE SOLAR WIND: OBSERVATIONS AND LINEAR VLASOV ANALYSIS
• Physics
• 2012
Kinetic microinstabilities in the solar wind arise when the plasma deviates too far from thermal equilibrium. Previously published work has provided strong evidence that the cyclotron, mirror, and
Proton core temperature effects on the relative drift and anisotropy evolution of the ion beam instability in the fast solar wind
• Physics
• 2002
[1] Typical nonthermal features of ion velocity distributions observed in the fast solar wind are the relative streaming between two proton components, an alpha/proton relative flow, and anisotropic
Consequences of proton and alpha anisotropies in the solar wind: Hybrid simulations
• Physics
• 2002
[1] Alfven fluctuations propagating away from the Sun in the solar corona and solar wind transfer energy via cyclotron resonances to ions of successively larger charge-to-mass ratios. This can yield
Alfvén‐cyclotron scattering of solar wind ions: Hybrid simulations
• Physics
• 2005
[1] This paper describes results from ensembles of hybrid simulations of steady, homogeneous, collisionless plasmas characterized by average solar wind parameters near 1 AU upon which damped,
Solar wind plasma: Kinetic properties and micro- instabilities
The kinetic properties of ions in the solar wind plasma are studied. Observations of solar wind H and He by the Faraday Cup instrument component of the Solar Wind Experiment on the Wind spacecraft
Physics-based Tests to Identify the Accuracy of Solar Wind Ion Measurements: A Case Study with the Wind Faraday Cups
• Physics
• 2006
[1] We present techniques for comparing measurements of velocity, temperature, and density with constraints imposed by the plasma physics of magnetized bi-Maxwellian ions. Deviations from these
Solar wind protons: Three-dimensional velocity distributions and derived plasma parameters measured between 0.3 and 1 AU
• Physics
• 1982
A survey of solar wind three-dimensional proton velocity distributions as measured by the Helios solar probes between 0.3 and 1 AU is presented. A variety of nonthermal features like temperature
Proton/alpha magnetosonic instability in the fast solar wind
• Physics
• 2000
A proton/alpha magnetosonic instability is investigated in the framework of the linear theory of plasma waves for conditions typical of the fast solar wind. Warm streaming alpha particles with a
Heating and acceleration of coronal ions interacting with plasma waves through cyclotron and Landau resonance
• Physics
• 2001
On the basis of quasi-linear theory, the parallel and perpendicular wave heating and acceleration rates for gyrotropic particle velocity distribution functions are derived. These rates can be used in