# 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, {tilde {beta}}{sub {parallel}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 {tilde {beta}}{sub {parallel}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 {tilde {beta}}{sub {parallel}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 {tilde {beta}}{sub {parallel}c} of theory is not inconsistent with a statistical lower bound on the observations of that parameter. {copyright} 1999 American Geophysical Union

- Authors:

- Los Alamos National Laboratory, Los Alamos, New Mexico (United States)
- Jet Propulsion Laboratory, Pasadena, California (United States)

- Publication Date:

- OSTI Identifier:
- 688001

- Resource Type:
- Journal Article

- Journal Name:
- Journal of Geophysical Research

- Additional Journal Information:
- Journal Volume: 104; Journal Issue: A9; Other Information: PBD: Sep 1999

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 66 PHYSICS; SOLAR WIND; WHISTLERS; HEAT TRANSFER; INTERPLANETARY SPACE; SOLAR WATER HEATERS; PLASMA INSTABILITY; WHISTLER INSTABILITY; ELECTRON-ION COLLISIONS; ELECTRON TEMPERATURE; HEAT FLUX; ASTROPHYSICS

### Citation Formats

```
Gary, S.P., Neagu, E., Skoug, R.M., and Goldstein, B.E.
```*Solar wind electrons: Parametric constraints*. United States: N. p., 1999.
Web. doi:10.1029/1999JA900244.

```
Gary, S.P., Neagu, E., Skoug, R.M., & Goldstein, B.E.
```*Solar wind electrons: Parametric constraints*. United States. doi:10.1029/1999JA900244.

```
Gary, S.P., Neagu, E., Skoug, R.M., and Goldstein, B.E. Wed .
"Solar wind electrons: Parametric constraints". United States. doi:10.1029/1999JA900244.
```

```
@article{osti_688001,
```

title = {Solar wind electrons: Parametric constraints},

author = {Gary, S.P. and Neagu, E. and Skoug, R.M. and Goldstein, B.E.},

abstractNote = {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, {tilde {beta}}{sub {parallel}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 {tilde {beta}}{sub {parallel}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 {tilde {beta}}{sub {parallel}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 {tilde {beta}}{sub {parallel}c} of theory is not inconsistent with a statistical lower bound on the observations of that parameter. {copyright} 1999 American Geophysical Union},

doi = {10.1029/1999JA900244},

journal = {Journal of Geophysical Research},

number = A9,

volume = 104,

place = {United States},

year = {1999},

month = {9}

}