Direct Evidence of Instability-Driven Constraints on Helium Temperature Anisotropies in the Solar Wind
Abstract
Since its launch in 1994, the Solar Wind Experiment (SWE) on the Wind spacecraft has made in situ measurements of protons (ionized hydrogen) and alpha-particles (fully-ionized helium) in the solar wind. Prior analysis of SWE data has focused on solar wind protons and shown that their temperature and temperature anisotropy are both regulated by the action of plasma microinstabilities. We now report on our major revisions to the code that processes raw SWE measurements that focused on optimizing the analysis of alpha-particles. Using this refined data set, we found that (contrary to conventional wisdom) kinetic instabilities also develop in solar wind alpha-particles. Since we exclusively analyzed collisionally young plasma, our results indicate that instabilities develop independently among the protons and alpha-particles despite the low fractional abundance of the latter. Additionally, we used linear dispersion theory to simulate the effects of microinstabilities on a two-component plasma and compare these results to those from our empirical work.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFMSH51C..05M
- Keywords:
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- 7827 SPACE PLASMA PHYSICS / Kinetic and MHD theory;
- 7829 SPACE PLASMA PHYSICS / Kinetic waves and instabilities;
- 7839 SPACE PLASMA PHYSICS / Nonlinear phenomena