1. Physics Faculty, National Research Tomsk State University, 36 Lenin Ave., 634050 Tomsk, Russia
2. Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation (IZMIRAN), 142190 Troitsk, Moscow, Russia
3. Institute of Physics, University of São Paulo, CP 66318, CEP 05315-970 São Paulo, SP, Brazil