Logo image
Back
Electron heat flow in the solar corona: Implications of non‐Maxwellian velocity distributions, the solar gravitational field, and Coulomb collisions
Journal article   Open access   Peer reviewed

Electron heat flow in the solar corona: Implications of non‐Maxwellian velocity distributions, the solar gravitational field, and Coulomb collisions

John C Dorelli and Jack D Scudder
Journal of Geophysical Research: Space Physics, Vol.108(A7), pp.1294-n/a
07/2003
DOI: 10.1029/2002JA009484
url
https://doi.org/10.1029/2002JA009484View
Published (Version of record) Open Access

Abstract

It has long been known that weak electron temperature gradients in fully ionized plamas (satisfying λ ∣∇Te∣/Te ≲ 10−4, where λe is the electron mean free path and Te is the electron temperature) can lead to the development of significant non‐Maxwellian suprathermal tails on electron velocity distributions, invalidating the Spitzer and Härm [1953] perturbation theory [Gray and Kilkenny, 1980; Bell et al., 1981; Scudder and Olbert, 1983]. In this paper we work out the implications of such nonlocal heat flow for electrons in the solar corona, comparing a new analytical theory to numerical solutions of the Fokker‐Planck equation. While electron‐electron Coulomb collisions are strong enough at coronal densities to influence the local temperature, the electron heat flux is determined by the essentially collisionless high‐energy tail. The deceleration of suprathermal electrons in the polarization electric field allows electron heat to flow radially outward against the local temperature gradient, in contrast to the local thermodynamic equilibrium picture, in which heat is constrained to flow down the local temperature gradient. We discuss the implications of this effect for empirical constraints of coronal heating mechanisms.
 electron heat flux Fokker‐Planck equation kappa distribution nonequilibrium thermodynamics nonlocal heat flow solar corona

Details

Metrics

20 Record Views
20 Times Cited - Web of Science
Logo image