Linear Correlation Between Radial and Normal Component Fluctuations of the Interplanetary Magnetic Field

IF 2.7 3区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS
Munetoshi Tokumaru, Nishiki Nozaki, Ken’ichi Fujiki
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Abstract

The interplanetary magnetic field (IMF), particularly its north–south component, acts as a key parameter for controlling the space weather effect of solar wind disturbances on the Earth; therefore, accurate understanding of the behavior of the IMF is important for improvement of space weather prediction. This study reports the relation between radial (\(B_{r}\)) and normal (\(B_{n}\)) components of IMF by analyzing in situ observations collected by inner- and outer-heliosphere spacecraft over multiple solar cycles. A quadratic relation between \(B_{r}\) and \(B_{n}\) with a 22-year periodicity which corresponds to the magnetic polarity cycle of the Sun was observed in IMF data of the inner-heliosphere spacecraft. In contrast, IMF data of the outer-heliosphere spacecraft did not show such a quadratic relation but exhibited a linear relation between \(B_{r}\) and \(B_{n}\) with a slope and correlation coefficient depending on the latitude: positive and negative slopes (correlation coefficients) were revealed from the IMF data for north and south latitudes, respectively, and those magnitudes increased with the latitude. Slopes and correlation coefficients of the linear relation depended on neither the radial distance nor the solar activity. The same linear relation between \(B_{r}\) and \(B_{n}\) was found for the IMF data of the inner-heliosphere spacecraft by sorting them into two groups in terms of the latitude. Therefore, quadratic relation was ascribed to the combined effect of the latitude variation of the inner-heliosphere spacecraft and the latitude dependence of the linear relation. Although the physical process to generate the linear relation remains an open question, some kind of MHD waves may be responsible for it.

行星际磁场的径向和正向分量波动之间的线性关系
行星际磁场,特别是其南北分量,是控制太阳风扰动对地球的空间天气影响的关键参数;因此,准确了解国际货币基金组织的行为对提高空间天气预报具有重要意义。本研究通过分析多个太阳活动周期内、外日球层航天器收集的现场观测资料,报告了IMF径向分量(\(B_{r}\))与正向分量(\(B_{n}\))之间的关系。在内日球层航天器的IMF数据中观测到\(B_{r}\)和\(B_{n}\)之间具有22年周期的二次关系,与太阳的磁极周期相对应。相比之下,外日球层航天器的IMF数据并没有表现出这种二次关系,而是表现出\(B_{r}\)和\(B_{n}\)之间的线性关系,其斜率和相关系数随纬度的变化而变化:IMF数据在北纬和南纬分别显示出正斜率和负斜率(相关系数),且随纬度的增加而增加。线性关系的斜率和相关系数与径向距离和太阳活动无关。通过将内日球层航天器的IMF数据按纬度分为两组,发现了\(B_{r}\)和\(B_{n}\)之间同样的线性关系。因此,二次关系是内日球层航天器的纬度变化和线性关系的纬度依赖性的综合作用。虽然产生线性关系的物理过程仍然是一个悬而未决的问题,但某种MHD波可能是造成这种关系的原因。
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来源期刊
Solar Physics
Solar Physics 地学天文-天文与天体物理
CiteScore
5.10
自引率
17.90%
发文量
146
审稿时长
1 months
期刊介绍: Solar Physics was founded in 1967 and is the principal journal for the publication of the results of fundamental research on the Sun. The journal treats all aspects of solar physics, ranging from the internal structure of the Sun and its evolution to the outer corona and solar wind in interplanetary space. Papers on solar-terrestrial physics and on stellar research are also published when their results have a direct bearing on our understanding of the Sun.
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