Effects of the major sudden stratospheric warming event of 2009 on the subionospheric very low frequency/low frequency radio signals
Effects of the major sudden stratospheric warming event of 2009 on the subionospheric very low frequency/low frequency radio signals
复制标题
2009年重大平流层突发变暖事件对亚电离层甚低频/低频无线电信号的影响
DOI：
10.1002/2016ja023813
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
S. Pal,Y. Hobara,S. K. Chakrabarti and P. W. Schnoor
中科院分区：
文献类型：
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作者：
西澤篤;及川康;片田敏孝;S. Pal,Y. Hobara,S. K. Chakrabarti and P. W. Schnoor
本文研究了2009年平流层重大突发变暖事件（SSW）对电离层下甚低频/低频（VLF/LF）无线电信号在地-电离层波导中传播的影响。研究了德国和日本的VLF/LF无线电网络接收到的与SSW事件相对应的4个发射机的信号幅度，以探讨高纬到中纬电离层可能的异常和大气影响。在SSW事件期间，VLF/LF信号的夜间和白天振幅在10 hPa平流层温度上升的所有传播路径上都有显著的异常增加或减少，增加或减少幅度为103 - 5dB。白天和夜间VLF/LF振幅的增加或减少实际上是由于低电离层边界条件在电子密度和电子中性碰撞频率分布方面的修改以及SSW期间不同传播波导模式之间的相关模式干扰效应。TIMED/SABER使命的数据也被用来调查在同一时期的VLF/LF传播路径的上层中层条件。我们观察到的中性温度下降，在75-80公里的高度附近的事件的峰值时间的压力增加。VLF/LF异常与平流层温度和中层气压变化相关且同相，而中层最低冷却值与VLF/LF异常最大值之间存在2-3天的延迟。使用地球电离层波导内的长波传播能力（LWPC）程序对VLF/LF日变化进行了模拟，以定性地解释VLF/LF异常。
This paper presents effects of the major sudden stratospheric warming (SSW) event of 2009 on the subionospheric very low frequency/low frequency (VLF/LF) radio signals propagating in the Earth‐ionosphere waveguide. Signal amplitudes from four transmitters received by VLF/LF radio networks of Germany and Japan corresponding to the major SSW event are investigated for possible anomalies and atmospheric influence on the high‐ to middle‐latitude ionosphere. Significant anomalous increase or decrease of nighttime and daytime amplitudes of VLF/LF signals by ∼3–5 dB during the SSW event have been found for all propagation paths associated with stratospheric temperature rise at 10 hPa level. Increase or decrease in VLF/LF amplitudes during daytime and nighttime is actually due to the modification of the lower ionospheric boundary conditions in terms of electron density and electron‐neutral collision frequency profiles and associated modal interference effects between the different propagating waveguide modes during the SSW period. TIMED/SABER mission data are also used to investigate the upper mesospheric conditions over the VLF/LF propagation path during the same time period. We observe a decrease in neutral temperature and an increase in pressure at the height of 75–80 km around the peak time of the event. VLF/LF anomalies are correlated and in phase with the stratospheric temperature and mesospheric pressure variation, while minimum of mesospheric cooling shows a 2–3 day delay with maximum VLF/LF anomalies. Simulations of VLF/LF diurnal variation are performed using the well‐known Long Wave Propagating Capability (LWPC) code within the Earth‐ionosphere waveguide to explain the VLF/LF anomalies qualitatively.