Santolík Ondřej, Kolmašová Ivana
Department of Space Physics, Institute of Atmospheric Physics, The Czech Academy of Sciences, Prague, Czechia.
Faculty of Mathematics and Physics, Charles University, Prague, Czechia.
Sci Rep. 2017 Oct 24;7(1):13948. doi: 10.1038/s41598-017-13849-4.
All lightning strokes generate electromagnetic pulses -atmospherics- which can travel over distances of thousands of kilometers. Night-side atmospherics show typical frequency dispersion signatures caused by sub-ionospheric propagation. Their analysis can be used to determine the distance to the source lightning, and therefore it represents a safe tool for investigation of distant thunderstorms, as well as for indirect observations of the lower ionosphere. However, such analysis has never been done on the dayside. Here we present the first results which show unusual daytime atmospherics with dispersion signatures originating from strong thunderstorms which occurred during winter months 2015 in the North Atlantic region. Using newly developed analysis techniques for 3-component electromagnetic measurements we are able to determine the source azimuth and to attribute these rare atmospherics to both positive and negative lightning strokes in northern Europe. We consistently find unusually large heights of the reflective ionospheric layer which are probably linked to low fluxes of solar X rays and which make the dayside subionospheric propagation possible. Although the atmospherics are linearly polarized, their dispersed parts exhibit left handed polarization, consistent with the anticipated continuous escape of the right-hand polarized power to the outer space in the form of whistlers.
所有闪电都会产生电磁脉冲——天电，其可传播数千公里。夜间天电呈现出由电离层下传播引起的典型频率色散特征。对其进行分析可用于确定闪电源的距离，因此它是研究远距离雷暴以及间接观测低层电离层的一种安全工具。然而，尚未在白天进行过此类分析。在此，我们展示了首个结果，其显示出具有色散特征的异常白天天电，这些特征源自2015年冬季在北大西洋地区发生的强烈雷暴。通过使用新开发的用于三分量电磁测量的分析技术，我们能够确定源方位，并将这些罕见的天电归因于北欧的正、负闪电。我们一致发现反射电离层的高度异常大，这可能与太阳X射线的低通量有关，并且使得白天电离层下传播成为可能。尽管天电是线偏振的，但其色散部分呈现左旋偏振，这与预期的右旋偏振功率以哨声形式持续逃逸到外层空间相一致。
