First observations of electron gyro-harmonic effects under X-mode HF pumping the high latitude ionospheric F-region
First observations of electron gyro-harmonic effects under X-mode HF pumping the high latitude ionospheric F-region
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DOI：
10.1016/j.jastp.2017.02.003
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发表时间：
2017-03
影响因子：
1.9
通讯作者：
N. Blagoveshchenskaya;T. Borisova;A. Kalishin;T. Yeoman;I. Häggström
中科院分区：
文献类型：
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作者：
N. Blagoveshchenskaya;T. Borisova;A. Kalishin;T. Yeoman;I. Häggström
我们提供了第一个实验证据的异常（X-模式）极化HF高功率无线电波的泵频率跨越第五电子回旋谐波（5 fce）从下到上的步进引起的现象的敏感性。结果是在Tromsweetern附近的EISCAT（欧洲非相干散射科学协会）HF加热器设施中获得的，有效辐射功率为456-715 MW，当HF泵浦波被传输到磁天顶时。我们分析了在远离加热器、高频增强等离子体和离子线处观测到的窄带受激电磁发射（SEE）谱中各种谱线的行为和强度（HFPL和HFIL）来自EISCAT UHF非相干散射雷达光谱，以及来自CUTLASS的人工场对准不规则性（英国合作双定位极光探测系统）观测，取决于泵场相对于5 fce的频率偏移。在低于5 fce的泵浦频率下，窄带SEE谱表现出非常强烈的所谓受激离子伯恩斯坦散射（SIBS），伴随着与受激布里渊散射（SBS）相关的其他谱分量，这些谱分量在5 fce附近被极大地抑制和消失，并且在fH> 5 fce时没有重新出现。当抽运频率达到5 fce时，HFPL和HFIL功率突然增强，等离子体谱线出现级联线，CUTLASS后向散射功率开始增加。这与5 fce附近的普通模式（O模式）效应相反。在第五电子回旋谐波的频率之下和附近的X-模式泵浦清楚地表明了从初始相互作用高度产生的诱导等离子体和离子线的上升高度，而对于O-模式加热的相互作用区域下降。当fH<5 fce时，电子沿磁场沿着和沿磁场的加速同时存在，而当fH≥ 5 fce时，电子沿磁场的加速沿着很强。
We provide the first experimental evidence of the sensitivity of phenomena induced by extraordinary (X-mode) polarized HF high power radio waves to pump frequency stepping across the fifth electron gyro-harmonic (5fce) from below to above. The results were obtained at the EISCAT (European Incoherent Scatter Scientific Association) HF heater facility near Tromsø under effective radiated powers of 456–715 MW, when the HF pump wave was transmitted into the magnetic zenith. We have analyzed the behavior and intensities of various spectral lines in the narrowband stimulated electromagnetic emission (SEE) spectra observed far from the heater, HF-enhanced plasma and ion lines (HFPL and HFIL) from EISCAT UHF incoherent scatter radar spectra, and artificial field-aligned irregularities from CUTLASS (Co-operative UK Twin Located Auroral Sounding System) observations, depending on the frequency offset of the pump field relative to the 5fce. At pump frequencies below 5fce the narrowband SEE spectra exhibited very intense so-called stimulated ion Bernstein scatter (SIBS), accompanied by other spectral components, associated with stimulated Brillouin scatter (SBS), which are greatly suppressed and disappeared in the vicinity of 5fce and did not reappear at fH>5fce. As the pump frequency reached 5fce, the abrupt enhancements of the HFPL and HFIL power, the appearance of cascade lines in the plasma line spectra, and the onset of increasing CUTLASS backscatter power occurred. That is opposite to the ordinary mode (O-mode) effects in the vicinity of 5fce. The X-mode pumping at frequencies below and in the vicinity of the fifth electron gyro-harmonic clearly demonstrated an ascending altitude of generation of induced plasma and ion lines from the initial interaction height, whereas for O-mode heating the region of interaction descended. The observations are consistent with the coexistence of the electron acceleration along and across the geomagnetic field at fH<5fce, while only very strong electron acceleration along the magnetic field was observed at fH≥5fce.