Toward an Integrated View of Ionospheric Plasma Instabilities: 3. Explicit Growth Rate and Oscillation Frequency for Arbitrary Altitude
Toward an Integrated View of Ionospheric Plasma Instabilities: 3. Explicit Growth Rate and Oscillation Frequency for Arbitrary Altitude
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DOI：
10.1029/2019ja026584
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发表时间：
2019-07
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通讯作者：
R. Makarevich
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作者：
R. Makarevich
推导了电离层等离子体不稳定性（包括法利-布尼曼不稳定性（FBI）和梯度漂移不稳定性（GDI））产生的不稳定等离子体波在离子坐标系ωr′中的增长率γ和振荡频率的一般解析表达式.在局部近似下，给出了任意高度和尺度下的显式表达式。仔细考虑了适用性的限制，重点是对电子密度梯度G= n/n和波长λ的依赖性。结果表明，控制适用性的关键参数是归一化到离子碰撞频率νi的生长速率γ，所开发的表达式对于缓慢生长γ/νi<0.1是有效的。它还表明，通常使用的假设，即波相速度Vph和等离子体漂移速度Vd的等效性，在F区的梯度弱到G=10− 5 m −1。开发的任意高度/尺度的解析表达式提供了一种协调各种高度和尺度特定情况的简单方法（例如，在E区的FBI/GDI模式），经常被忽视的离子惯性显示出在和解中发挥关键作用。新的离子惯性效应可以用增长率表达式中的量νi2+ωr′2−1表示。发现该效应降低标准FBI因子并放大GDI因子，并且由于与离子惯性成反比关系，该效应在较大的高度和/或波长处逐渐变强。
General analytic expressions are derived for the growth rate γ and oscillation frequency in the ion frame ωr′ 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 νi, with the developed expressions being valid for slow growths γ/νi<0.1. It is also shown that the commonly used assumption about the equivalency of the wave phase velocity Vph and the plasma drift velocity Vd fails in the F region at gradients as weak as G=10−5m−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 quantity νi2+ωr′2−1 in 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.