The CHAOS-7 geomagnetic field model and observed changes in the South Atlantic Anomaly.
The CHAOS-7 geomagnetic field model and observed changes in the South Atlantic Anomaly.
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DOI：
10.1186/s40623-020-01252-9
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Kuvshinov A
中科院分区：
文献类型：
--
作者：
Finlay CC;Kloss C;Olsen N;Hammer MD;Tøffner-Clausen L;Grayver A;Kuvshinov A
本文根据近地轨道卫星Swarm、CryoSat-2、CHAMP、SAC-C和Ehrsted的磁场观测资料，以及地面观测资料月平均值的年际差异，建立了1999 - 2020年近地地磁场随时间变化的CHAOS-7模型。CHAOS-7模型包括一个随时间变化的内部场，球谐度为20，一个静态内部场，合并到LCS-1岩石圈场模型超过25度，磁层场及其感应对应模型，描述卫星矢量磁力计对准的欧拉角估计，以及CryoSat-2磁力计校准参数。在磁场估计中只使用了符合严格的地磁静止时间标准（包括IMF和所有纬度的条件）的暗区数据。模型参数估计使用迭代重加权正则化最小二乘程序;与以前版本的混沌模型相比，在高球谐度下放松了随时间变化的内部场的正则化。我们使用CHAOS-7来调查地磁场的近期变化，研究自2014年以来南大西洋弱场异常和太平洋地区快速场变化的演变。在地球表面，南大西洋异常的第二个最小值现在在非洲西南部很明显。绿色函数的核幔边界径向场的表面强度表明，这一功能是连接到南非下的反向通量功能的移动和演化。主异常的持续增长和减弱与南美洲下方反向通量的向西运动和聚集有关。在2015年至2018年期间，地球表面的太平洋地区，磁场径向分量的二阶时间导数（加速度）发生了符号变化。这种加速度变化采取局部的、东西向的偶极形式。它在地面上被清楚地记录下来，例如在檀香山的地磁观测站，在太平洋中部和西部的一个扩展区域的蜂群观测中也看到了。继续向下延伸到核幔边界，我们发现该事件起源于2017年中太平洋和西太平洋低纬地区的场加速度变化。
We present the CHAOS-7 model of the time-dependent near-Earth geomagnetic field between 1999 and 2020 based on magnetic field observations collected by the low-Earth orbit satellites Swarm, CryoSat-2, CHAMP, SAC-C and Ørsted, and on annual differences of monthly means of ground observatory measurements. The CHAOS-7 model consists of a time-dependent internal field up to spherical harmonic degree 20, a static internal field which merges to the LCS-1 lithospheric field model above degree 25, a model of the magnetospheric field and its induced counterpart, estimates of Euler angles describing the alignment of satellite vector magnetometers, and magnetometer calibration parameters for CryoSat-2. Only data from dark regions satisfying strict geomagnetic quiet-time criteria (including conditions on IMF and at all latitudes) were used in the field estimation. Model parameters were estimated using an iteratively reweighted regularized least-squares procedure; regularization of the time-dependent internal field was relaxed at high spherical harmonic degree compared with previous versions of the CHAOS model. We use CHAOS-7 to investigate recent changes in the geomagnetic field, studying the evolution of the South Atlantic weak field anomaly and rapid field changes in the Pacific region since 2014. At Earth’s surface a secondary minimum of the South Atlantic Anomaly is now evident to the south west of Africa. Green’s functions relating the core–mantle boundary radial field to the surface intensity show this feature is connected with the movement and evolution of a reversed flux feature under South Africa. The continuing growth in size and weakening of the main anomaly is linked to the westward motion and gathering of reversed flux under South America. In the Pacific region at Earth’s surface between 2015 and 2018 a sign change has occurred in the second time derivative (acceleration) of the radial component of the field. This acceleration change took the form of a localized, east–west oriented, dipole. It was clearly recorded on ground, for example at the magnetic observatory at Honolulu, and was seen in Swarm observations over an extended region in the central and western Pacific. Downward continuing to the core–mantle boundary, we find this event originated in field acceleration changes at low latitudes beneath the central and western Pacific in 2017.
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影响因子：
3
作者：
Finlay, Christopher C.;Olsen, Nils;Toffner-Clausen, Lars
通讯作者：
Toffner-Clausen, Lars
影响因子：
5.3
作者：
Davies, Christopher J.;Constable, Catherine G.
通讯作者：
Constable, Catherine G.
影响因子：
5.2
作者：
Grayver, A. V.;Munch, F. D.;Toffner-Clausen, L.
通讯作者：
Toffner-Clausen, L.
影响因子：
3
作者：
Olsen, N;Lowes, F;Sabaka, TJ
通讯作者：
Sabaka, TJ
DOI：
10.1111/j.1365-246x.1988.tb03433.x
发表时间：
1988-07-01
期刊：
GEOPHYSICAL JOURNAL-OXFORD
影响因子：
--
作者：
CONSTABLE, CG
通讯作者：
CONSTABLE, CG