The ionospheric response to geomagnetic storms is usually investigated by considering the variability of the critical frequency of the F2-layer (foF2) or the total electron content (TEC) because these two parameters are directly measured by the ionosonde stations and the Global Navigation Satellite Systems (GNSS). In the present paper, however, the reaction is explored by using the vertical profiles of the electron density, N(h), reconstructed by manually scaled ionosonde measurements at the station Sofia (42.4°N, 23.2°E). The mid-latitude ionosheric response to three geomagnetic storms that occurred in January 2005 is presented as this period has been selected because no major sudden stratospheric warming occurred during this month, and the winter 2005 is given in the literature as an example of a “normal” year. Hence the observed ionospheric response to the considered geomagnetic storms can be attributed mainly to the external forcing. Besides the traditional parameters foF2 and TEC, a particular attention is paid to the variability of the peak electron density height (hmF2). This study reveals for the first time that the main contribution to the response of the midlatitude ionosphere to moderate/intense winter geomagnetic storms is associated with significant enhancements of short-period quasi-diurnal oscillations with period of 6–7 hours observed in both foF2 and hmF2. An explanation of the main mechanisms responsible for the distortion of the diurnal ionospheric variability during these storms is offered. This result is especially important for the ground-based HF radio communications.

通常通过考虑F2层临界频率（foF2）或总电子含量（TEC）的可变性来研究电离层对地磁暴的响应，因为这两个参数是由电离探空仪台站和全球导航卫星系统直接测量的（GNSS）。然而，在本文中，通过使用电子密度N（h）的垂直分布图来探索反应，该垂直分布图是通过在索非亚站（42.4°N，23.2°E）手动缩放的离子探空仪测量值重建的。由于选择了这一期间，是因为选择了这个时期，因此呈现了对2005年1月发生的三场地磁风暴的中纬度电渗响应，并且在文献中将2005年冬季作为“正常”的例子。 “ 年。因此，观测到的电离层对考虑的地磁风暴的响应可以主要归因于外部强迫。除了传统参数foF2和TEC，还要特别注意峰值电子密度高度（hmF2）的可变性。这项研究首次揭示了对中纬度电离层对中/强冬季磁暴的响应的主要贡献与在foF2和foF2观测到的6-7小时的短周期准日振荡的显着增强有关。 hmF2。提供了解释这些风暴期间昼夜电离层变异性失真的主要机制。该结果对于基于地面的HF无线电通信尤为重要。