Research on the Measurement Nonstationarity of Geomagnetic Variation Field Based on HHT Transform

摘要

The calculation formula of nonstationarity measure based on Hilbert-Huang transform (HIT)in time domain is identified in this article.To further investigate the nonstationary variation characteristics of the geomagnetic variation field,the nonstationarity measure for time series based on HHT is used to analyze the degree of nonstationarity (DN) ofz component.The data used in this article is the z component with different K-indexes.The result indicates that with the increase of the degree of the disturbance of the geomagnetic variation field,the DN of z component becomes increasingly larger and varies more fiercely.