1. Geophysical Research Department, A.V. Gaponov-Grekhov Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod 603950, Russia
2. Department of Geophysics, Tel Aviv University, Tel Aviv 69978, Israel
3. Rapid Telecom Systems Labs LLC, Nizhny Novgorod 603104, Russia
4. Department of Applied Mathematics, Nizhny Novgorod State Technical University, n.a. R.E. Alekseev, Nizhny Novgorod 603155, Russia