[M-IS08] Interdisciplinary studies on pre-earthquake processes

[MIS08-P07] Correlations between geomagnetic Sq external and internal equivalent current systems in East-Asia and Oceania regions

*Xiaocan Liu¹、Peng Han⁴、Katsumi Hattori^2,3、Huaran Chen¹、Chie Yoshino² (1.Institute of geophysics China Earthquake Administrition、2.Graduate School of Science, Chiba University, Chiba, Japan、3.Center for Environmental Remote Sensing, Chiba University, Chiba, Japan、4.Department of Earth and Space Sciences, Southern University of Science and Technology, ShenZhen, China)

キーワード：Sq external current, Sq internal current, correlation, East-Asia and Oceania regions

Abstract Geomagnetic Sq variation, namely the solar quiet daily variation [Campbell, 1989; Xu, 2003; Yamazaki, 2009], originates from the dynamo currents (external source current) at about an altitude of 100km in the ionosphere and the induced currents (internal source current) generated underground by the external source current [Chapman and Bartels, 1940; Chapman, 1951; Kane, 1976; Xu, 2003]. The Sq variations recorded by the ground stations contain total geomagnetic effects produced by the two current systems. The Sq currents deduced from the data of ground geomagnetic observatories are called Sq equivalent current systems. Most previous studies focused on kinds of the variations for the two Sq current systems. So far, we don't know what the consistency of the activities for the two parts current systems is, whether they are completely the same, or there are differences.

In present work, the absolute values of geomagnetic three components (XYZ) data from 20 observatories in East-Asia and Oceania regions were used to investigate the correlations between the external and internal Sq current systems. The seasonal current models of D (northern winter) season, E (equinox) season, and J (northern summer) season have been constructed by SHA (Spherical Harmonic Analysis) respectively. The intra-seasonal correlations of the current vortex center parameters T (local time), Φ (latitude), J (current intensity) between the Sq equivalent internal and external currents are analyzed. The results show that (1) in the E season, the correlation of T is the highest, the square of correlation coefficients is R²=0.857 in the NH (northern hemisphere). (2) And in the local summer and winter, the correlation of J is the strongest. The square of correlation coefficients are R²= 0.490 and 0.778, respectively, and also in the NH.

The mechanism for different seasonal correlations of different current vortex center parameters between the external and internal current systems is roughly considered. In fact, as two parts of the same current system, solar activity, ionospheric conductivity, neutral wind field, geomagnetic field and so on affect the internal and external current systems. At the same time, the variations of internal current are also controlled by the conductivity of underground conductive circle in the upper mantle. [Schmucker 1970; Campbell 1987, Campbell and Schiffmacher, 1988].