Simultaneous rocket probe and radar measurements of equatorial spread F—Transitional and short wavelength results
Simultaneous rocket probe and radar measurements of equatorial spread F—Transitional and short wavelength results
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同时火箭探测器和雷达测量赤道扩散 F——过渡和短波长结果
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发表时间：
1982
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影响因子：
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通讯作者：
R. Tsunoda
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作者：
M. Kelley;R. Pfaff;K. Baker;J. Ulwick;R. Livingston;C. Rino;R. Tsunoda
在从夸贾林岛起飞的PLUMEX I火箭飞行期间，在0.96米和0.36米波长的地面雷达后向散射测量的同时，现场测量了等离子体密度和电场波动。火箭穿透了一个极其动荡的顶部区域，这与强烈的后向散射有关。根据雷达的测量，后向散射功率在飞行期间和飞行后随着时间的推移而衰减。中波长(0.1-10公里)的原位电子密度测量在附文中描述，而在这里我们报告了过渡波和短波长的结果(λ<；100m)。这些数据包括首次对波长小于1m的静电起伏的电场分量进行了赤道扩展F的现场测量.在280m以上的所有高度，电子密度和波长小于100m的电场起伏的波数谱都有一个可重复的形式.密度谱的变化近似为k−5，电场谱的变化近似为k−3.密度谱的陡度对应于密度波形在100m或更小的尺度上没有陡峭的边缘.这两种谱形式与涉及与磁场平行的有限波数的低频波(k∥)的解释是一致的。理论和实验室实验都表明，负折射率梯度驱动漂移波的密度涨落谱在4.5-6.0之间。由于这种波确实具有有限的k∥，并且由于在扩展F环境中存在陡峭的梯度，我们得出结论，在足够高的高度，漂移波作用于由主要的较长波长不稳定性引起的陡峭的梯度，从而产生观察到的光谱形式。正如Huba和Ossakow(1981b)所讨论的那样，这些波可能会产生反常扩散。在较低的海拔，在几十米范围内观测到了较浅的光谱指数，这可能与碰撞的衰减机制有关。这表明漂移波的高度阈值可能与离子中性碰撞有关。幂定律谱在k⊥ri≈1附近没有明显变化，其中ri是离子回旋半径。由于k⊥ri≳1的低频漂移波是线性稳定的，似乎波-波相互作用(级联)的作用是在波线性衰减的范围内储存能量。K⊥Re≳0.2的光谱变化(较小的负指数)可能是由于低杂波漂移波的激发，并可能与观测到的1m量级的后向散射增强有关.稳定性分析表明，在背向散射最强烈的区域，等离子体位于低杂波漂移波的边缘稳定边界附近，但处于稳定的一侧.在没有漂移波的地区，有证据表明在200米波长处存在指数级内尺度截止。
During the PLUMEX I rocket flight from Kwajalein Island, plasma density and electric field fluctuations were measured in situ, simultaneous with ground-based radar backscatter measurements at 0.96-m and 0.36-m wavelengths. The rocket penetrated an extremely turbulent topside region which had associated intense backscatter. As measured by the radar the backscatter power was decaying with time during and after the flight. The intermediate wavelength (0.1–10 km) in situ electron density measurements are described in a companion paper, while here we report the transitional and short wavelength results (λ < 100 m). These data include the first in situ equatorial spread F measurements of the electric field component of electrostatic fluctuations with wavelengths less than 1 m. At all altitudes above about 280 km, a repeatable form for the wave-number spectrum was found for the electron density and electric field fluctuations at wavelengths less than about 100 m. The density spectrum varies approximately as k−5 and the electric field spectrum as k−3. The steepness of the density spectrum corresponds to an absence of steep edges in the density waveform on the scale of 100 m and less. These two spectral forms are shown to be consistent with an explanation involving low-frequency waves with finite wave numbers parallel to the magnetic field (k∥). Both theory and laboratory experiments show a power law density fluctuation spectrum for gradient-driven drift waves with negative index in the range 4.5–6.0. Since such waves do have finite k∥, and since sharp gradients exist in the spread F environment, we conclude that at sufficiently high altitudes, drift waves act on the steep gradients caused by a primary longer-wavelength instability to create the observed spectral form. These waves may then create an anomalous diffusion as discussed by Huba and Ossakow (1981b). At lower altitudes a shallower spectral index was observed in the tens of meters range, which may be related to a collisional damping regime. This suggests an altitude threshold for the drift waves that is probably related to ion neutral collisions. The power law spectra show no marked change near k⊥ri ≈ 1 where ri is the ion gyroradius. Since low-frequency drift waves are linearly stable for k⊥ri ≳ 1, it seems that a wave-wave interaction (cascade) operates to deposit energy in a range where waves are linearly damped. There is a slight suggestion of a spectral change (smaller negative index) for k⊥re ≳ 0.2 which may be due to excitation of a lower-hybrid drift wave and which may be related to the observed enhanced backscatter at wavelengths on the order of 1 m. A stability analysis shows that the plasma is near but on the stable side of the marginal stability boundary for the lower-hybrid drift wave in the most intense region of backscatter. In regions devoid of drift waves, evidence is found for an exponential inner-scale cutoff at a wavelength of 200 m.