Observations of E region irregularities generated at auroral latitudes by a high‐power radio wave
Observations of E region irregularities generated at auroral latitudes by a high‐power radio wave
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高功率无线电波在极光纬度产生的 E 区不规则现象的观测
DOI：
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发表时间：
1985
期刊：
影响因子：
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通讯作者：
B. Thidé
中科院分区：
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作者：
F. Djuth;R. J. Jost;S. T. Noble;W. E. Gordon;P. Stubbe;H. Kopka;E. Nielsen;R. Boström;H. Derblom;Å. Hedberg;B. Thidé
1983年9月，在斯堪的纳维亚利用位于挪威特罗姆瑟附近的高频加热设施进行了一系列电离层改造实验。这些实验旨在研究强高频无线电波在极光E区产生的地磁场方向不规则现象。在这份初步报告中，3.2米的不规则性与移动的46.9兆赫的现场雷达的意见。当电离层条件正确时，在特罗姆瑟上空的E区会激发出峰值截面约为104平方米的不规则体。目前的结果是一致的理论研究表明，它是更容易产生短尺度的磁场排列的不规则性在地磁倾角是大的位置。当46.9 MHz高频感应雷达回波较强时，回波功率的e折叠增长时间一般在50 ~ 150 ms之间，而当特罗姆瑟上空E区回波较弱时，其增长周期可达数秒~数十秒。由高频波产生的不规则体在时间和空间上常常表现出动态结构。在一般情况下，观察提供实验支持的不稳定性理论，采用附近的上混合共振的相互作用，以驱动人工的不规则性。结果还表明，自然发生的不规则性有时可能在激发HF引起的极光E区的不规则性中发挥关键作用。可能需要额外的过程来解释较慢的不规则增长率经常观察到的雷达回波时，相对较弱，偶尔观察到，即使相对较强的信号。
In September 1983 a series of ionospheric modification experiments was performed in Scandinavia using the high-frequency (HF) heating facility located near Tromso, Norway. The experiments were designed to study the production of geomagnetic field-aligned irregularities in the auroral E region by a powerful HF radio wave. In this initial report, observations of 3.2-m irregularities made with a mobile 46.9-MHz field radar are presented. When ionospheric conditions are correct, irregularities having peak cross sections of about 104 m² are excited in the E region over Tromso. The present results are consistent with theoretical studies which indicate that it is easier to generate short-scale field-aligned irregularities at locations where the geomagnetic dip angle is large. When the HF-induced radar echo at 46.9 MHz is strong, the e-folding growth times of the echo power are typically between 50 and 150 ms. However, when the E region echo over Tromso is weak, the growth period can range from seconds to tens of seconds. The irregularities generated by the HF wave often exhibit dynamic structure both in time and in space. In general, the observations provide experimental support for instability theories that employ interactions near the upper hybrid resonance to drive the artificial irregularities. The results also indicate that naturally occurring irregularities may at times play a key role in the excitation of HF-induced irregularities in the auroral E region. Additional processes are probably required to explain the slower irregularity growth rates often observed when radar echoes are relatively weak and occasionally observed even for relatively strong signals.