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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Lower Ionosphere Sensitivity to Solar X-ray Flares Over a Complete Solar Cycle Evaluated From VLF Signal Measurements
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Lower Ionosphere Sensitivity to Solar X-ray Flares Over a Complete Solar Cycle Evaluated From VLF Signal Measurements

机译：在从VLF信号测量中评估的完整太阳循环中，对太阳X射线的较低电离层敏感性

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The daytime lower ionosphere behaves as a solar X-ray flare detector, which can be monitored using very low frequency (VLF) radio waves that propagate inside the Earth-ionosphere waveguide. In this paper, we infer the lower ionosphere sensitivity variation over a complete solar cycle by using the minimum X-ray fluence (F_(Xmin)) necessary to produce a disturbance of the quiescent ionospheric conductivity. F_(Xmin) is the photon energy flux integrated over the time interval from the start of a solar X-ray flare to the beginning of the ionospheric disturbance recorded as amplitude deviation of the VLF signal. F_(Xmin) is computed for ionospheric disturbances that occurred in the time interval of December-January from 2007 to 2016 (solar cycle 24). The computation of F_(Xmin) uses the X-ray flux in the wavelength band below 0.2 nm and the amplitude of VLF signals transmitted from France (HWU), Turkey (TBB), and U.S. (NAA), which were recorded in Brazil, Finland, and Peru. The main result of this study is that the long-term variation of F_(Xmin) is correlated with the level of solar activity, having F_(Xmin) values in the range (1-12) × 10~(-7) J/m~2. Our result suggests that F_(Xmin) is anticorrelated with the lower ionosphere sensitivity, confirming that the long-term variation of the ionospheric sensitivity is anticorrelated with the level of solar activity. This result is important to identify the minimum X-ray fluence that an external source of ionization must overcome in order to produce a measurable ionospheric disturbance during daytime.
机译：白天降低电离层的表现为太阳X射线闪光检测器，可以使用在地球电离层波导内传播的非常低频（VLF）无线电波来监测。在本文中，我们通过使用所需的最小X射线流量（F_（Xmin））来推断出完整的太阳能循环的较低的电离层敏感性变化来产生静态电离层导电性的干扰。 F_（Xmin）是从太阳X射线开始的时间间隔集成到从太阳X射线的开始到截止电离层扰动的开始，记录为VLF信号的幅度偏差。 F_（XMIN）计算于2007年至2016年12月至2016年12月至2016年的时间间隔（太阳循环24）的电离层扰动。 F_（XMIN）的计算使用波长带中的X射线通量低于0.2nm，以及从法国（HWU），土耳其（TBB）和美国（NAA）传输的VLF信号的幅度，该幅度在巴西记录，芬兰和秘鲁。本研究的主要结果是F_（XMIN）的长期变化与太阳能活动水平相关，在范围（1-12）×10〜（-7）j /中具有f_（xmin）值。/ m〜2。我们的结果表明，F_（Xmin）具有较低的电离层敏感性，确认电离层敏感性的长期变化与太阳能的水平反对。该结果对于识别必须克服外部电离源的最小X射线流量是重要的，以便在白天产生可测量的电离层扰动。

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