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Toward an Integrated View of Ionospheric Plasma Instabilities: 3. Explicit Growth Rate and Oscillation Frequency for Arbitrary Altitude
Author(s) -
Makarevich Roman A.
Publication year - 2019
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2019ja026584
Subject(s) - collision frequency , physics , instability , oscillation (cell signaling) , inertia , wavelength , plasma , ionosphere , plasma oscillation , drift velocity , growth rate , computational physics , ion , altitude (triangle) , atomic physics , mechanics , classical mechanics , geophysics , quantum mechanics , chemistry , mathematics , geometry , biochemistry
General analytic expressions are derived for the growth rate γ and oscillation frequency in the ion frameω r ′of unstable plasma waves generated by ionospheric plasma instabilities including the Farley‐Buneman instability (FBI) and the gradient‐drift instability (GDI). The explicit expressions are developed for arbitrary altitude and scales in the local approximation. Limits of applicability are carefully considered focusing on the dependence on the electron density gradients G =∇ n / n and wavelengths λ . It is shown that the key parameter that controls the applicability is the growth rate γ normalized to the ion collision frequency ν i , with the developed expressions being valid for slow growths γ / ν i <0.1. It is also shown that the commonly used assumption about the equivalency of the wave phase velocity V ph and the plasma drift velocity V d fails in the F region at gradients as weak as G =10 −5 m −1 . The developed analytic expressions for arbitrary altitude/scale offer a straightforward way of reconciling various altitude‐ and scale‐specific cases (e.g., FBI/GDI modes in the E region), with the often‐neglected ion inertia shown to play a critical role in the reconciliation. The new ion inertia effect is found to be represented by the quantityν i 2 + ω r ′ 2− 1in the growth rate expression. The effect is found to reduce the standard FBI factor and amplify the GDI factor, and, due to the inverse relationship with the ion inertia, the effect becomes progressively stronger at larger altitudes and/or wavelengths.