Seasonal and longitudinal effects on plasmaspheric tube content

A mathematical model of the ionosphere and plasmasphere that includes an eccentric dipole geomagnetic field has been constructed to model, in the first instance, whistler results at L = 2.5. Observations show that there is a pronounced annual variation in plasmaspheric tube content at mid-latitudes and that this effect is modulated by longitude. The model results indicate that the geometry of the magnetic field (in terms of geographic coordinates) is a major factor in determining the magnitude of the annual variation, with neutral air winds and the degree of plasmaspheric refilling also important. A global variation in neutral atomic hydrogen abundance appears to have little influence.