Optical remote sensing of the thermosphere with HF pumped artificial airglow
Optical remote sensing of the thermosphere with HF pumped artificial airglow
复制标题
利用高频泵浦人工气辉进行热层光学遥感
DOI：
10.1029/1999ja000366
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发表时间：
2000
影响因子：
--
通讯作者：
E. Sergeev
中科院分区：
文献类型：
--
作者：
P. Bernhardt;M. Wong;J. Huba;B. Fejer;L. S. Wagner;J. Goldstein;C. Selcher;V. Frolov;E. Sergeev
电离层中高功率无线电波激发的光发射可用于测量热层中的各种参数。强大的高频 (HF) 无线电波在 F 区域反射的区域产生高能电子。这些热或超热电子与原子氧原子碰撞，产生亚稳态 O(1D) 和 O(1S) 原子的局部区域。这些亚稳态随后分别辐射 630.0 和 557.7 nm，产生 HF 泵浦人工气辉 (HPAA) 云。 HPAA云的形状由自然发生或电离层加热过程中形成的大范围（约10公里）等离子体不规则结构决定。当高频波连续工作时，气辉云的运动遵循等离子体的 E × B 漂移。当高频波关闭时，气辉云会因碰撞猝灭和辐射而衰减，因中性扩散而膨胀，并因中性风而漂移。使用连续和步进无线电波传输获得的 HPAA 云图像经过处理后可产生高层大气中的电场、中性风矢量和扩散系数。该技术使用 1993 年 3 月和 1995 年在俄罗斯下诺夫哥罗德附近的电离层修改设施获得的数据进行了说明。 HPAA 云分析得出夜间向东 70 m s−1 的纬向等离子体漂移。根据 260 km 处产生的高能电子的人工气辉，纬向中性风速估计为 96 m s−1，O(1D) 扩散系数确定为 0.8 至 1.4 × 1011 cm2 s−1 之间。 O(1D) 的淬火寿命确定为 29.4 s。扩散和淬灭速率与热层中的原子和分子浓度直接相关。如果增加人工气辉发射的强度，则可以获得遥感技术的改进。尝试采用脉冲序列和调谐近电子回旋加速器谐波的高功率无线电传输来增加光发射。然而，这两种方法都会降低强度，因此，以远离电子陀螺谐波的频率进行连续传输是优选的加热方式。
Optical emissions excited by high-power radio waves in the ionosphere can be used to measure a wide variety of parameters in the thermosphere. Powerful high-frequency (HF) radio waves produce energetic electrons in the region where the waves reflect in the F region. These hot or suprathermal electrons collide with atomic oxygen atoms to produce localized regions of metastable O(1D) and O(1S) atoms. These metastables subsequently radiate 630.0 and 557.7 nm, respectively, to produce clouds of HF pumped artificial airglow (HPAA). The shapes of the HPAA clouds are determined by the structure of large-scale (≈10 km) plasma irregularities that occur naturally or that develop during ionospheric heating. When the HF wave is operated continuously, the motion of the airglow clouds follows the E × B drift of the plasma. When the HF wave is turned off, the airglow clouds decay by collisional quenching and radiation, expand by neutral diffusion, and drift in response to neutral winds. Images of HPAA clouds, obtained using both continuous and stepped radio wave transmissions, are processed to yield the electric fields, neutral wind vectors, and diffusion coefficients in the upper atmosphere. This technique is illustrated using data that were obtained in March 1993 and 1995 at the ionospheric modification facility near Nizhny Novgorod, Russia. Analysis of HPAA clouds yields zonal plasma drifts of 70 m s−1 eastward at night. On the basis of artificial airglow from energetic electrons generated at 260 km the zonal neutral wind speed was estimated to be 96 m s−1 and the O(1D) diffusion coefficient was determined to be between 0.8 and 1.4 × 1011 cm2 s−1. The quenched lifetime of the O(1D) was determined to be 29.4 s. The diffusion and quenching rates are directly related to the atomic and molecular concentrations in the thermosphere. Improvements in the remote-sensing technique may be obtained if the intensity of the artificial airglow emissions is increased. High-power radio transmissions employing pulse sequences and tuning near electron cyclotron harmonics were attempted to increase the optical emissions. Both of these, however, produced reduced intensity, and consequently, continuous transmission at frequencies away from electron gyro harmonics is the preferred heating regime.