Solar wind electrons: Parametric constraints
Abstract
Solar wind electrons are often observed to consist of two distinguishable components, a thermal, more dense core and a suprathermal, less dense halo. In this core/halo model linear Vlasov theory for the whistler heat flux instability predicts dimensionless heat flux thresholds which decrease as the electron core beta, β~∥c, increases. It has been proposed that this theoretical threshold corresponds to an observable upper bound on the electron heat flux. Linear theory also predicts that there is a critical value of β~∥c below which the whistler heat flux instability does not have appreciable growth in the solar wind; there is another suggestion that this corresponds to an observable lower bound on β~∥c. These two proposals are examined by comparison of linear theory and data from the initial in-ecliptic phase of the Ulysses mission. The instability threshold does provide a statistical constraint on observed solar wind heat fluxes, and the critical β~∥c of theory is not inconsistent with a statistical lower bound on the observations of that parameter.
- Publication:
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Journal of Geophysical Research
- Pub Date:
- September 1999
- DOI:
- 10.1029/1999JA900244
- Bibcode:
- 1999JGR...10419843G
- Keywords:
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- Interplanetary Physics: Solar wind plasma