Thermal effects in the ionospheric plasma instabilities including the Farley‐Buneman instability (FBI), the gradient‐drift instability (GDI), and the ion‐thermal instability (ITI) are analyzed, focusing on analytic analysis of the previously obtained general expression of the combined instability growth rate. It is shown that thermal effects lead to generally nonmonotonic behavior of the growth rate with the background electric field
This content will become publicly available on October 1, 2024
This paper develops a unified linear theory of cross field plasma instabilities, including the Farley–Buneman, electron thermal, and ion thermal instabilities, in spatially uniform collisional plasmas with partially unmagnetized multi-species ions. Collisional plasma instabilities in weakly ionized, highly dissipative, weakly magnetized plasmas play an important role in the lower Earth's ionosphere and may be of importance in other planetary ionospheres, stellar atmospheres, cometary tails, molecular clouds, accretion disks, etc. In the Earth's ionosphere, these collisional plasma instabilities cause intense electron heating. In the solar chromosphere, they can do the same—an effect originally suggested from spectroscopic observations and modeling. Based on a simplified 5-moment multi-fluid model, the theoretical analysis presented in this paper produces the linear dispersion relation for the combined Thermal Farley–Buneman Instability with an important long-wavelength limit analyzed in detail. This limit provides an easy interpretation of different instability drivers and wave dissipation. This analysis of instability, combined with simulations, will enable us to better understand plasma waves and turbulence in these commonly occurring collisional space plasmas.
more » « less- Award ID(s):
- 2149781
- NSF-PAR ID:
- 10490156
- Publisher / Repository:
- Physics of Plasmas
- Date Published:
- Journal Name:
- Physics of Plasmas
- Volume:
- 30
- Issue:
- 10
- ISSN:
- 1070-664X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract or, equivalently with the plasma drift speed , in contrast with the conventional quadratic (FBI) or linear (GDI) dependence. The threshold electric field for FBI is demonstrated to exist at all altitudes, although at higher altitudes and/or at longer wavelength the threshold fields become too high to be observed in the ionosphere. The GDI growth rate is shown to be significantly modified by the thermal effects at long wavelengths. In the absence of thermal effects, the growth rate is proportional to a cosine of the flow angle, the angle between the differential plasma drift and the wavevector. Thermal effects result in an additional phase shift that maximizes at an altitude around 120 km, using representative high‐latitude ionospheric parameters, and in an increase in the proportionality coefficient by up to a factor of 2. The study highlights the usefulness of an analytic treatment for revealing additional insights into the instability behavior in the broad range of ionospheric parameters that may remain hidden using only numerical treatment. -
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