Electric field measurements of DC and long wavelength structures associated with sporadic-E layers and QP radar echoes
Electric field measurements of DC and long wavelength structures associated with sporadic-E layers and QP radar echoes
复制标题
DOI：
10.5194/angeo-23-2319-2005
复制
发表时间：
2005-10
影响因子：
1.9
通讯作者：
R. Pfaff;H. Freudenreich;T. Yokoyama;M. Yamamoto;S. Fukao;H. Mori;S. Ohtsuki;N. Iwagami
中科院分区：
文献类型：
--
作者：
R. Pfaff;H. Freudenreich;T. Yokoyama;M. Yamamoto;S. Fukao;H. Mori;S. Ohtsuki;N. Iwagami
抽象的。电场和等离子体密度数据收集的探空火箭从日本内浦航天中心发射，揭示了一个复杂的电动力学与零星的E层和准周期雷达回波的同时观测。电动力学的特点是空间和时间的变化，火箭的上升段和下降段穿越低电离层之间有很大的不同。在上升段的主要零星E层（95-110 km）内，电场是可变的，振幅为2-4 mV/m，在1-3 km的高度间隔内变化很大。与等离子体密度增强和/或耗尽相一致的极化电场的识别并不明显。然而，在这一区域的下降段，电场的方向显示出显着的变化，正好与一个单一的，狭窄的零星的- E等离子体密度层的峰值附近102.5公里。这一切变可能与中性风切变有关，中性风切变是造成该层形成的原因。从110 km到火箭远地点152 km的上升段上零星的E层上方的电场数据揭示了一系列连续的明显的、大尺度的准周期结构，其波长为10-15 km，波矢在NE-SW象限之间取向。电场结构具有3-5 mV/m的典型振幅，其中一个振幅为9 mV/m，并且在非常一般的意义上，与等离子体密度的扰动相关。电场波形显示出变陡和/或收敛效应的证据，并推测已从下方零星的- E区域沿着磁场向上映射。解释这些结构起源的候选机制包括Kelvin-Helmholtz不稳定性和E s层不稳定性。在这两种情况下，形成零星- E层的相同剪切将提供产生km尺度结构的能量。其他可能性包括重力波或这些过程的组合。这些数据表明，这些结构与低海拔密度条纹，同时观察到的QP雷达回波的座位。它们似乎也与中性风数据中定义明确的“螺旋”模式的机制有关，这些数据在15分钟后发射的第二枚探空火箭释放的化学踪迹中被揭示。短尺度（E区110 km以下）。不规则性在上升管上被组织成2-3层，其中等离子体密度也显示出多层，但在下降管上被限制在单层，其中等离子体密度显示出单个的、明确定义的零星- E峰。涉及直流电场和垂直等离子体梯度的线性梯度漂移不稳定性被证明是无法驱动所观察到的波的upleg，但可能有助于增长的短尺度波的顶部上的狭窄的不稳定的密度梯度上观察到的downleg。这些数据表明，自由能的其他来源可能是短尺度不规则性增长的重要因素。关键词电离层（中纬度电离层;电场和电流;电离层不规则性）
Abstract. Electric field and plasma density data gathered on a sounding rocket launched from Uchinoura Space Center, Japan, reveal a complex electrodynamics associated with sporadic- E layers and simultaneous observations of quasi-periodic radar echoes. The electrodynamics are characterized by spatial and temporal variations that differed considerably between the rocket's upleg and downleg traversals of the lower ionosphere. Within the main sporadic- E layer (95–110 km) on the upleg, the electric fields were variable, with amplitudes of 2–4 mV/m that changed considerably within altitude intervals of 1–3 km. The identification of polarization electric fields coinciding with plasma density enhancements and/or depletions is not readily apparent. Within this region on the downleg, however, the direction of the electric field revealed a marked change that coincided precisely with the peak of a single, narrow sporadic- E plasma density layer near 102.5 km. This shear was presumably associated with the neutral wind shear responsible for the layer formation. The electric field data above the sporadic- E layer on the upleg, from 110 km to the rocket apogee of 152 km, revealed a continuous train of distinct, large scale, quasi-periodic structures with wavelengths of 10–15 km and wavevectors oriented between the NE-SW quadrants. The electric field structures had typical amplitudes of 3–5 mV/m with one excursion to 9 mV/m, and in a very general sense, were associated with perturbations in the plasma density. The electric field waveforms showed evidence for steepening and/or convergence effects and presumably had mapped upwards along the magnetic field from the sporadic- E region below. Candidate mechanisms to explain the origin of these structures include the Kelvin-Helmholtz instability and the E s -layer instability. In both cases, the same shear that formed the sporadic- E layer would provide the energy to generate the km-scale structures. Other possibilities include gravity waves or a combination of these processes. The data suggest that these structures were associated with the lower altitude density striations that were the seat of the QP radar echoes observed simultaneously. They also appear to have been associated with the mechanism responsible for a well-defined pattern of "whorls" in the neutral wind data that were revealed in a chemical trail released by a second sounding rocket launched 15min later. Short scale ( E region below 110km. The irregularities were organized into 2–3 layers on the upleg, where the plasma density also displayed multiple layers, yet were confined to a single layer on the downleg where the plasma density showed a single, well-defined sporadic- E peak. The linear gradient drift instability involving the DC electric field and the vertical plasma gradient is shown to be incapable of driving the observed waves on the upleg, but may have contributed to the growth of short scale waves on the topside of the narrow unstable density gradient observed on the downleg. The data suggest that other sources of free energy may have been important factors for the growth of the short scale irregularities. Keywords. Ionosphere (Mid-latitude ionosphere; Electric fields and currents; Ionospheric irregularities)