1. Institute of Mathematics and PhysicsSiedlce University Siedlce Poland
2. ReSoLVE Centre of ExcellenceUniversity of Oulu Oulu Finland
3. Sodankylä Geophysical ObservatoryUniversity of Oulu Oulu Finland
4. Ioffe Physical‐Technical Institute St. Petersburg Russia
5. Department of Physics and Astronomy University of Hawai‘i at Mānoa Honolulu Hawaii USA