Open AccessLong‐term features of drifting and standing non‐dipole fields as determined from Holocene palaeomagnetic secular variations
Author(s) -
Itota Chizu,
Hyodo Masayuki,
Yaskawa Katsumi
Publication year - 1997
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.1997.tb05655.x
Subject(s) - secular variation , earth's magnetic field , geology , clockwise , geodesy , paleomagnetism , dipole , geophysics , geomagnetic secular variation , term (time) , magnetic field , physics , amplitude , optics , quantum mechanics , geomagnetic storm
SUMMARY Geomagnetic field motions of Holocene secular variations are investigated using a separation method. The palaeomagnetic secular variations from Britain, North America and Australia have been subjected to maximum‐entropy method analyses. Based on the results of spectral analyses, the secular variations are separated by band‐pass filters into low‐frequency components, generally including the period band 1800‐3600 yr, and high‐frequency components, generally including the period band 1000‐1200 yr. There is an interval, from 4200 to 1700 yr BP, which shows clockwise rotational motions in the low‐frequency components of all three sites. Westward drifting of geomagnetic fields may be globally dominant. Swinging or elliptical looping motions constrained to a certain direction were observed in the low‐frequency components of the British data. The time duration for the persistence of the swinging motion constrained to a certain direction was 3500 years or so, which could be the lifetime of an oscillating stationary field. The duration of the transitional motion was 1000‐1300 years, which may indicate the recurrence time of a stationary field.