Search for: All records

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. 

Abstract Increased precipitation in the Arctic is a robust feature across model simulations of the coming century, driven by intensification of meridional moisture transport and enhanced local evaporation in the absence of sea ice. These mechanisms are associated with distinct, seasonal, spatial, and, likely, precipitation isotope (δ²H_Precip) expressions. Historical observations of δ²H_Precipreveal a contrast in seasonality between southwestern and northwestern coastal Greenland: δ²H_Precipin northwestern Greenland varies in phase with local temperature, whereas δ²H_Precipin southwestern Greenland is decoupled from local temperature and exhibits little seasonal variation. We test the hypothesis that reduced δ²H_Precipseasonality in southwestern Greenland relative to northwestern Greenland results from dynamic moisture source variations, by diagnosing monthly average moisture sources to three sink regions (Kangilinnguit, Ilulissat, and Qaanaaq) using the Water Accounting Model‐2layers model. All domains demonstrate strong intra‐annual moisture source variations. Moisture to the southernmost region is sourced most remotely in summer and most locally in winter, associated with stronger cooling from the source in summer than winter, promoting more negative δ²H_Precipand counteracting local temperature‐driven seasonality. In comparison, moisture transport distance to the northernmost region is relatively constant, as local sea ice restricts northward migration of the winter moisture source. We simulate seasonal patterns in δ²H_Precipin a simple Rayleigh model, which confirm the importance of source temperature and starting isotopic compositions in determining δ²H_Precipfor these regions. δ²H_Precipsensitivity to moisture source variability suggests these coastal Arctic settings may yield paleoclimate records sensitive to the moisture transport processes predicted to amplify future precipitation.