Winter anomaly in NmF2 and TEC: when and where it can occurYury V. Yasyukevich, Anna S. Yasyukevich, Konstantin G. Ratovsky, Maxim V. Klimenko, Vladimir V. Klimenko and Nikolay V. ChirikJ. Space Weather Space Clim., 8 (2018) A45DOI: https://doi.org/10.1051/swsc/2018036