The whistler heat flux instability: Threshold conditions in the solar wind

Journal Article · Thu Dec 01 04:00:00 EST 1994 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/94JA02067· OSTI ID:91320

Gary, S P; Scime, E E; Phillips, J L; Feldman, W C ^[1]

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1. Los Alamos National Lab., NM (United States)

Solar wind electrons are observed often to consist of two components: a core and a halo. The anisotropies and relative average speeds of these two components correspond to a heat flux that has the potential to excite several different electromagnetic instabilities; wave-particle scattering by the resulting enhanced fluctuations can limit this heat flux. This manuscript describes theoretical studies using the linear Vlasov dispersion equation for drifting bi-Maxwellian component distributions in a homogeneous plasma to examine the threshold of the whistler heat flux instability. Expressions for this threshold are obtained from two different parametric baselines: a local model that yields scalings as functions of local dimensionless plasma parameters, and a global model based on average electron properties observed during the in-ecliptic phase of the Ulysses mission. The latter model yields an expression for the heat flux at threshold of the whistler instability as a function of heliospheric radius that scales in the same way as the average heat flux observed from Ulysses and that provides an approximate upper bound for that same quantity. This theoretical scaling is combined with the observational results to yield a semiempirical closure relation for the average electron heat flux in the solar wind between 1 and 5 AU. 29 refs., 9 figs., 2 tabs.

• OSTI ID: 91320
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A12 Vol. 99; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ELECTRONS
HEAT FLUX
SOLAR WIND
WHISTLER INSTABILITY