Ionospheric Electron Density Gradients of a Polar Region Using GPS

The ionosphere gradient plays a significant part in parameters extraction and high precisionpositioning.Due to its special form,the gradient of the polar ionosphere is most complicated.Forwide areas,based on the assumption of a thin shell and the dependence on elevation for the mappingfunction,mapping function errors can be obtained by a subtraction of coinciding pierce points,thenthis can be used to detect ionosphere gradients.Meanwhile,TEC maps of different areas and time areobtained by regional ionosphere model.For local areas,the horizontal gradients of two IPPs are ob-tained along with longitude and latitude.Results show that during magnetic storm ionosphere gradi-ents of mid-latitude and polar region increase remarkably.But during magnetic quiet time,however incomparison with the stability of gradients of the mid-latitudes,gradients in the polar region are stillactive.This illustrates that the special morpha of polar ionosphere results in the instability of gradi-ents.