The Potential Impacts of the Erratic Motion of Dip Equator and Magnetic Poles

摘要

This paper examined the secular displacement of the dip equator and the geomagnetic poles as well as the variations of the global magnetic inclination and declination angles using magnetometer measurements onboard different low-Earth orbit (LEO) satellite. The secular variation of the dip equator and geomagnetic poles has different impacts on different applications-from affecting the long-term characterization of the low-latitude ionosphere to degrading the precision of geomagnetic navigation. The strong displacement of the dip equator can result in a systematic error in the determination of the long-term equatorial electric field variations and hence in the characterization of ionospheric density structure, especially in the region, where the displacement of dip equator is large enough (more than 20 km or 0.2°/year) within the time scale of a solar cycle or less. Similarly, the slowly moving locations of magnetic poles, estimated from magnetometer observations onboard LEO satellite, exemplify noticeable discrepancy with that of world magnetic model (WMM) and International Geomagnetic Reference Field (IGRF) values, indicating inevitable possible impact on the precise geomagnetic navigation for commercial and military applications. Thus, accurately estimated locations of the dip equator and magnetic poles, as well as declination angles, are critically important.