Electrostatic noise in non‐Maxwellian plasmas: Generic properties and “kappa” distributions

Abstract

We study the generic properties of the electrostatic noise spectrum measured by an antenna immersed in a plasma with an isotropic electron velocity distribution function, at frequencies of the order of magnitude of the plasma frequency. We find that at high frequencies the noise level is proportional to the electron pressure for long wire antennae and to the electron flux for long double‐sphere antennae. At low frequencies it depends mostly on the low‐energy electrons. We also study the shape of the peak near the plasma frequency, for distribution functions with Maxwellian or power law high‐energy tails. We calculate the noise produced with a generalized Lorenzian (“kappa”) distribution function and compare the results with those obtained with different distributions having the same density and equivalent temperature. We deduce some practical consequences for plasma wave measurements in space.

Comment on “Mathematical and physical aspects of Kappa velocity distribution” [Phys. Plasmas 14, 110702 (2007)]

“…͑8͒, i.e., they 51 use the same form for the temperature as we have discussed above. 3,14 As we have seen, that agrees with the form used in Ref. 10 and the many papers that follow it.…”

“…6,14,25 As an aside, we note that integration over two velocity space coordinates leads to the one-dimensional kappa distribution function, 10,27,38 which can be written as…”

Nonequilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind (Invited Review)

“…It is important to note that the Debye length L D , which is determined by the low-energy particles, is defined from L denoting the average of the inverse square speed (see, e.g., Meyer-Vernet, 1993), so that (Chateau and Meyer-Vernet, 1991)…”

Suprathermal Particle Populations in the Solar Wind and Corona

“…The quasi-thermal noise spectroscopy is a powerful tool for in situ space plasma diagnostics based on the analysis of the electrostatic field spectrum produced by the quasi-thermal fluctuations of electrons (Chateau & Meyer-Vernet, 1991;Le Chat et al, 2009;Zouganelis, 2008). The quasi-thermal noise is produced by the quasi-thermal fluctuations of the electrons and by the Doppler-shifted thermal fluctuations of the ions.…”