This paper reports disturbance in the mid-latitude sub-ionospheric VLF radio signals due to the super geomagnetic storm which began on 17 March 2015. Narrow-band signals from the NAA transmitter are studied for the storm period recorded at eight mid-latitude receiving stations spread over the Europe and USA. Daytime signals amplitude at all places showed a disturbing pattern after 17 March. Fluctuation in the nighttime signals significantly increased in the succeeding nights. As a primary effect of the storm, the entire diurnal signals in the transoceanic west to east long propagation paths enhanced by 3–5 dB, which gradually decreased over the period of $~$10 days following the storm recovery. A different behavior was observed in the east to west short propagation paths over the landmass, where during the peak storm the daily variations of the VLF amplitude reduced to 20–25% of a normal day and, after $~$10 days the signals returned to the pre-storm condition. Modeling of the radio waves in the west to east paths shows that the D-region electron density was increased by $~$8-fold and varied up to 10 days. Electron density variations in the D-region closely follows the variations of precipitated electron flux as observed by the POES satellite over the region. The elevated electron density in the D-region ionosphere caused by the extension of the auroral precipitation to the mid-latitudes along with interference among the various waveguide modes in the earth-ionosphere waveguide during the storm is suggested for the cause of observed VLF signals behaviors.

本文报告了 2015 年 3 月 17 日开始的超级地磁风暴对中纬度亚电离层 VLF 无线电信号的干扰。研究了来自 NAA 发射机的窄带信号在八个中纬度接收站记录的风暴期间遍布欧洲和美国。3 月 17 日之后，所有地方的白天信号幅度都显示出令人不安的格局。在随后的夜晚，夜间信号的波动显着增加。作为风暴的主要影响，跨洋西向东长传播路径的整个昼夜信号增强了 3-5 dB，在$~$风暴恢复后 10 天。在陆地上从东到西的短传播路径中观察到不同的行为，在风暴高峰期间，VLF 振幅的每日变化减少到正常一天的 20-25%，之后$~$10 天后，信号恢复到风暴前的状态。从西到东路径的无线电波建模表明，D 区电子密度增加了$~$8 倍，变化长达 10 天。D 区的电子密度变化与 POES 卫星在该地区观测到的沉淀电子通量的变化密切相关。极光降水向中纬度地区的延伸以及风暴期间地球-电离层波导中各种波导模式之间的干扰导致 D 区电离层中电子密度的升高被认为是观测到的 VLF 信号行为的原因.