Estimation of westward drifting rate of non-dipole fields from Holocene geomagnetic secular variation

从全新世地磁长期变化估算非偶极子场西移速率

基本信息

批准号：
06640546
负责人：
HYODO Masayuki
金额：
$ 1.34万
依托单位：
Kobe University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06640546/
关键词：
Geomagnetic secular variation westward drifting geomagnetic field 古地磁気学

项目摘要

A record of the geomagnetic secular variation for the last about 20 ky was obtained from two sediment cores in Lake Qionghai, China. The following four geomagnetic phenomena were deduced from the record. 1) A maximum easterly swing is recorded around 3800yBP,being consistent with the westward drifting model by Hyodo (1993). 2) A rate of 0.14ﾟ/y is newly estimated for westward drifting of a large non-dipole source. 3) A geomagnetic excursion characterized by a large westerly swing is found around 18000 yBP.4) The excursion fields also show clockwise rotational sense of motion, suggesting that westward drifting of non-dipole fields is dominant during the period.A geomagnetic secular variation record from Lake Erhai, China for the last 10 ky has no maximum easterly swing unlike the record from Lake Qionghai. In place, it shows that clockwise rotational motion is dominant from 4000-1700 yBP.This fact is consistent with Hyodo's model for westward drifting of a nondipole field. The absence of the easterly swing may be due to core-twisting. Short period components of the secular variation are well correlated with those of Lake Qionghai.Geomagnetic secular variation records during Holocene time are obtained from 13 areas in the world. Each record has different quality. The records from Britain, North America, and Australia are highly reliable because replicate records have been obtained from several cores. The geomagnetic field motions investigated by use of separation method (Itota et al., 1992) show that periodicities of 1100 and 2400 y/c are dominant at the three sites, and that clockwise rotations are dominant on the whole. Westward drifting rates estimated from the periodicities are 0.32ﾟ/y and 0.15 ﾟ/y. The latter is close to the rate 0.14ﾟ/y estimated from easterly swings.

从Qionghai湖中的两个沉积物核心获得了最后一个大约20个ky的记录。 0.14以4）的特征为tic tiC，这也显示了Clso旋转的旋转感。来自中国Erhai湖的地磁世俗变化记录，最后10个KY没有杰出的记录。顺时针运动在4000-1700 YBP中占主导地位。对于非枢纽场的向西漂移而言，这是一致的。从世界上的13个领域获得了变化的时间。 1100和2400 y/c在三个位置上占主导地位，并且顺时针旋转在周期性估计的向西漂移上是0.32 E 0.14°/y的0.14°/y估计，从东方的波动估计。