On the generation of modified low-frequency Farley-Buneman waves in the solar atmosphere

Abstract

The possibility of the excitation of Farley‐Buneman turbulence in the solar atmosphere is examined. It is found that the conditions for the generation of the modified Farley‐Buneman instability can be realized in the chromosphere of the Sun 1000 km above the photosphere. While usual Farley‐Buneman waves studied in relation to the Earth's ionosphere are almost electrostatic, the modified Farley‐Buneman waves in the solar atmosphere are electromagnetic ones. This means, that not only the potential electric field caused by the charge distribution, but also the perturbations of the magnetic field and the circularly‐polarized electric field are essential. Although the physical pictures of usual and modified Farley‐Buneman waves are different, their dispersion equations are almost the same. However, the increment of the modified Farley‐Buneman waves is varied by additional electromagnetic effects. It is demonstrated that electromagnetic effects hinder a Farley‐Buneman instability in occurring while ξ < 1, where ξ is the square of the ratio of ion plasma frequency times ion‐neutral frequency to ion‐cyclotron frequency times wave number times speed of light in vacuum. Under the condition ξ > 1, no Farley‐Buneman disturbances appear at all. In weakly‐ionized solar regions, the modified (ξ < 1) and also the usual (ξ ≪ 1) Farley‐Buneman turbulence could make “electromagnetic” contributions to the process of energy dissipation of nonstationary streams of neutral gases. Besides, they may modify the low‐frequency acoustic noise. It seems that the modified Farley‐Buneman turbulence contributes to the sporadic radiation of the Sun. It is possible, that such an effect takes not only place in the chromosphere of the Sun, but also in the atmospheres of other stars.

MAVEN Observations of Ionospheric Irregularities at Mars

“…The 1 s integration time for a single LPW I‐V sweep means, however, that these irregularities are not fully resolved in electron density. Electromagnetic Farley‐Buneman waves have been predicted to exist in the solar atmosphere (Liperovsky et al, ) but, to our knowledge, have not been reported elsewhere, and it is unclear whether the irregularities presented here are such waves or not.…”

Magnetosphere-ionosphere coupling throughEregion turbulence: 1. Energy budget

“…Our results apply to all regions that contribute to the total ionospheric conductances, from the top electrojet down to the potentially unstable D region [ Kelley , 2009]. Similar processes can occur in other plasma media, like the Solar chromosphere [ Liperovsky et al , 2000; Fontenla et al , 2008; Gogoberidze et al , 2009], other planetary ionospheres, and laboratory plasma [ D'Angelo et al , 1974; John and Saxena , 1975; Koepke , 2008], despite the dramatic differences in parameters. Last, these calculations for arbitrarily magnetized plasma serve as an additional verification of the general relations obtained in section 2 from first principles.…”

Farley-Buneman Instability in the Solar Chromosphere

“…Recent analysis of three dimensional vector currents and temperatures, deduced from spectropolarimetric observations of a sunspot from photospheric to chromospheric levels, has shown that, while resistive current dissipation can contribute to heat the sunspot chromosphere, it is not the dominant factor (Socas-Navarro 2007). Recently, it has been suggested that the Farley-Buneman (Farley 1963;Buneman 1963) instability (FBI), driven by convective motions, can be responsible for chromospheric heating (Liperovsky et al 2000;Fontenla 2005;Fontenla et al 2008).…”

“…Using the decrement of the FBI derived by (Farley 1963) and assuming a negligible ion magnetization, Fontenla et al (2008) concluded that the FBI should be present at least in the upper half of the chromosphere. Earlier, the analysis of Liperovsky et al (2000) had indicated that the FBI might operate in the chromosphere at heights h > 1000 km.…”