The spatial integration of transient ULF pulsations observed by ground based magnetometers

Abstract

The major source of damping for resonant ULF pulsations is thought to be joule dissipation in the conducting ionosphere. determined by the Pedersen conductance, Sp. Transient pulsations (i.e. short-lived pulsations with latitude-dependent periods) are toroidal mode oscillations of the geomagnetic field shells (Poulter & Nielsen 1982), and are often associated with SSC and SI. In this paper empirical models of the toroidal mode east-west Hall current density J were used to calculate the associated ground magnetic fields in an attempt to resolve the following points: (1) decay rates observed by ground magnetometers are in general larger than those observed by satellites and predicted by theory; (2) estimates of'the Pedersen conductance using ground magnetometer derived decay rates seem too low (Glassmeier et al. 1984); (3) ground magnetometer observations of transient pulsations may show little or no period variation with latitude (Allan et al. 1985); (4) the effect of non-monotonic latitudinal period variations (e.g. the plasmapause).