TY JOUR TI Ultra low frequency emissions ranging from 0.1 to 3 Hz in circumpolar areas KW ultra low frequency electromagnetic waves KW polar caps KW cusp KW magnetosphere KW solar wind JO Solnechno-Zemnaya Fizika AU Potapov, A.S. AU Guglielmi, A.V. AU Dovbnya, B.V. PY 2020 IS 6 PB INFRA-M Academic Publishing LLC.