Natural Electromagnetic Fields in Pure and Applied Geophysics / Естественные электромагнитные поля в прикладной геофизике

In this chapter, very brief scenarios of the complex interaction of solar radiations with the Earth’s magnetosphere are presented and the intricate origin of the (i) sferics, (ii) pulsations and micropulsations, (iii) variations of the extraterrestrial magnetic fields, (iv) Van Allen Radiation belts, (v) ionosphere, (vi) ring current, (vii) magnetopause, (viii) magnetic sheath, (ix) magnetotail and (x) magnetic storms are discussed. The various branches of geophysics, evolved because of this time varying natural source electromagnetics, are also discussed in reasonable detail. They are (i) telluric current methods (T), (ii) magnetotellurics (MT), (iii) audiofrequency magnetotellurics (AMT), (iv) geomagnetic depth sounding (GDS), (v) magnetometer array studies (MA), (vi) magneto-variational sounding (MVS), marine MT (MMT) and (vii) the audio-frequency magnetic method (AFMAG). A few controlled-source auxiliary tools that are used along with MT and AMT are: (i) controlled-source audio-frequency magnetotellurics (CSAMT), (ii) long/offset transient electromagnetics (LOTEM), (iii) marine controlled electromagnetic (CSEM) and radiomagnetotellurics (RMT). Brief discussions on mathematical modelling and inversion are included to touch upon the interpretational aspects of geophysical data. <...>