1. Joint Institute for High Temperatures, RAS, 13/2 Izhorskaya St., 125412 Moscow, Russia
2. Dukhov Research Institute of Automatics, 22 Sushchevskaya St., 127055 Moscow, Russia
3. L.D. Landau Institute for Theoretical Physics, RAS, 1A Ak. Semenova av, 142432 Chernogolovka, Russia