Non-magnetic aspect sensitive auroral echoes from the lower E region observed at 50 MHz
Non-magnetic aspect sensitive auroral echoes from the lower E region observed at 50 MHz
复制标题
在 50 MHz 下观察到的来自下 E 区域的非磁性方位敏感极光回波
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
K. Schlegel
中科院分区：
文献类型：
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作者：
R. Rüster;K. Schlegel
在挪威安多亚使用ALOMAR SOUSY雷达在接近90°的方位角（几乎平行于磁场方向）观测到E区不规则结构的后向散射。强电场和E区电子温度的增加，同时测量的非相干散射设施EISCAT证明，Farley-Buneman等离子体不稳定性激发。此外，强烈的粒子沉淀，从EISCAT电子密度推断，表明梯度漂移不稳定性可能是活跃的，太。在如此大的纵横角下的反向散射是不期望的，并且之前没有观察到。然而，观测到的回波的特征在许多方面与通常的极光雷达结果完全不同：多普勒速度仅为10 m/s的量级，频谱的半宽度约为5 m/s，回波起源于远低于100 km的高度，并且它们似乎对磁场方向不敏感。因此，我们的结论是，相应的不规则性不是由上述不稳定性引起的，必须援引其他机制。
Backscatter from E-region irregularities was observed at aspect angles close to 90° (almost parallel to the direction of the magnetic field) using the ALOMAR SOUSY radar at Andoya/Norway. Strong electric fields and increased E-region electron temperatures simultaneously measured with the incoherent scatter facility EISCAT proved that the Farley-Buneman plasma instability was excited. In addition, strong particle precipitation was present as inferred from EISCAT electron densities indicating that the gradient drift instability may have been active, too. Backscatter at such large aspect angles was not expected and has not been observed before. The characteristics of the observed echoes, however, are in many aspects completely different from usual auroral radar results: the Doppler velocities are only of the order of 10 m/s, the half-width of the spectra is around 5 m/s, the echoes originate at altitudes well below 100 km, and they seem to be not aspect-sensitive with respect to the magnetic field direction. We, therefore, conclude that the corresponding irregularities are not caused by the mentioned instabilities and that other mechanism have to be invoked.