Resonant compressional waves in the geomagnetic tail

Irregularities in the solar wind can excite compression waves in the geomagnetic tail that have their maximum amplitude in the plasma sheet. Details such as the exact frequency and spatial distribution of the waves depend on the over-all geometry of the tail. Estimates of these properties are obtained by use of a single-layered, two-dimensional model. Symmetric and antisymmetric modes are studied. For the physical parameters chosen to represent the ‘typical’ tail, the fundamental period of the antisymmetric mode is approximately 11 minutes and that of the symmetric mode is approximately 2 minutes. Other properties are discussed.