| 外源S_q等效电流体系电流涡中心电流强度与太阳活动关系 |
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| 引用本文： | 袁桂平,吴迎燕,张学民.外源S_q等效电流体系电流涡中心电流强度与太阳活动关系[J].地球物理学报,2015,58(10):3457-3468. |
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| 作者姓名： | 袁桂平 吴迎燕 张学民 |
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| 作者单位： | 1. 中国地震局地震预测研究所, 北京 100036;
2. 江苏省地震局, 南京 210014 |
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| 基金项目： | 国家高技术研究发展计划(863计划)(2012AA121004)资助. |
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| 摘 要： | 本文选取了INTERMAGNET地磁台网2001年到2012年的地磁数据,对其进行世界时(UT)到地方时(LT)的转换后利用自然正交分量法(NOC)从所选资料中提取出太阳静日变化Sq成分,再通过球谐分析方法建立模型分离内、外源Sq成分,逐日反演出内、外源Sq等效电流体系,并得到外源Sq等效电流体系南北电流涡中心电流强度.本文将外源Sq等效电流体系南北电流涡中心电流强度与同一时期的Dst指数进行了对比分析,研究表明它们之间具有同步变化的规律,且北半球电流涡中心电流强度在磁暴发生时的异常现象远高于南半球.对F10.7cm太阳射电流量与外源Sq等效电流体系南、北半球电流涡中心电流强度的长短周期分析发现,Sq等效电流表现出明显的11年周期特点,与太阳活动周期一致.外源南、北半球电流涡中心电流强度和F10.7cm年均值的相关系数分别达到了0.93和0.90,说明太阳活动是导致外源Sq电流体系变化的最直接也最主要的因素,这可能与电离层电导率受控于太阳的电磁辐射相关.
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| 关 键 词： | 太阳静日变化Sq 球谐分析 反演 外源场 |
| 收稿时间： | 2014-11-25 |
Relationship between the centric intensity of electric current in the external Sq equivalent current system and the solar activity |
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| YUAN Gui-Ping,WU Ying-Yan,ZHANG Xue-Min.Relationship between the centric intensity of electric current in the external Sq equivalent current system and the solar activity[J].Chinese Journal of Geophysics,2015,58(10):3457-3468. |
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| Authors: | YUAN Gui-Ping WU Ying-Yan ZHANG Xue-Min |
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| Institution: | 1. Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China;
2. Jiangsu Earthquake Administration, Nanjing 210014, China |
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| Abstract: | Solar quiet variation (Sq) is one of the typical variations of the geomagnetic field, also one of the basic laws of geophysics geomagnetic observation. Sq includes the external magnetic field derived from the generator current of the ionospheric E region and internal magnetic field which is from electromagnetic induction because of the conductivity of the Earth, which may also contain other magnetic disturbances. The Sq electric current system is the main electric current in the ionosphere when geomagnetic activity is calm. So, the Sq current system and its related research have great significance for the study of the magnetosphere and ionosphere. The purpose of this paper is to obtain internal and external Sq equivalent current systems, respectively,and to study the relationship of the external Sq equivalent current system and solar activity.
Gauss studied spherical harmonic analysis (SHA) and applied it to separate the internal and external geomagnetic fields. SHA is the general standard method for global modeling,which can fit known values and use measured values to calculate the value of the position which have no measured value. Many scholars of home and abroad use the SHA method to separate internal and external sources of Sq. Their studies found that external Sq electric current has no obvious change with universal time but internal Sq electric current has obvious change with universal time, and geographical latitude of the electric current vortices for both internal and external Sq electric currents have close relation with the magnetic equator. Geomagnetic data on the INTERMAGNET from 2001 to 2012 are analyzed in this paper. We use minutely values to obtain hour's values and transform hours values from universal time to local time. Using natural quadrature component method (NOC) to get Sq composition from hour's data, according to the previous study, we choose first order components to be Sq. After this, we use the SHA method to build a model for the inversion of internal and external Sq equivalent current systems. We can get diurnal drawing of internal and external Sq equivalent current systems and the current intensity of northern and southern vortex centers in these two systems. We also analyze the relationship between the current intensity at the vortex center of external Sq equivalent current system, the Dst index and F10.7 cm solar radio flow at the same time.
Comparing the Dst index and external Sq equivalent current system, we found that the current intensity in both the northern and southern hemisphere obviously increases then decreases. This trend shows that there is a synchronous change rule between current intensity and Dst index, and this phenomenon is more obvious in the northern hemisphere.
According to our results, Dst index and current intensity of the external Sq equivalent current system have similar characteristics, and this feature is more obvious in the year when the geomagnetic storm is larger and time is fewer. But the correlation coefficient of them on day-to-day is not high. Combining the classification of geomagnetic storms (classification:weak, medium, strong, violent, enormous;the Dst index lower limit: 30 nT, 50 nT, 100 nT, 200 nT, 350 nT) and the complexity of Sq,we think current intensity of the external Sq equivalent current system on both the southern and northern hemisphere will increase first and then decrease when the geomagnetic storm is not quiet. Both of current intensity and Dst index are classified in a big scope and undulate within a certain range. This feature makes their correlation coefficient not high. In the year of more geomagnetic storms, the geomagnetic storms have complex forms, long durations, and good global synchronicity. In addition, geomagnetic storms make ionospheric current have a disturbance and make electric current of Sq not stable enough. It might be the reason that the corresponding relationship between the geomagnetic storm and current intensity is more obvious in the years with more and bigger geomagnetic storms.
Sq equivalent current has a similar cycle (11 years) with solar activity. In this paper, we use current intensity of northern and southern vortex centers in external equivalent current systems to analyze the correlation with F10.7 cm. The correlation coefficients of their annual average in the southern and northern hemisphere are 0.93 and 0.90, respectively. These results show the external Sq current system is influenced by solar activity directly. This may be related to that the ionospheric conductivity is controlled by electromagnetic radiation of the sun. |
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| Keywords: | Solar quiet daily variation Sq Spherical harmonic analysis Inversion External magnetic field |
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