Long-term variation of radar-auroral backscatter and the interplanetary sector structure
Long-term variation of radar-auroral backscatter and the interplanetary sector structure
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雷达极光后向散射和行星际扇区结构的长期变化
DOI：
10.1029/ja095ia12p21123
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
T. Jones
中科院分区：
文献类型：
--
作者：
T. Yeoman;M. Burrage;M. Lester;T. Robinson;T. Jones
地磁活动在太阳自转周期和高次谐波周期约为27天的周期性变化是一个有据可查的现象。来自瑞典和英国雷达-极光实验（SABRE）雷达的极光雷达反向散射数据提供了从1981年至今的连续时间序列，这是地磁活动的高灵敏度监测器。本文利用最大熵方法（MEM）分析了1981 - 1989年SABRE后向散射数据的动态功率谱、1981 - 1987年行星际磁场和太阳风参数以及1932年以来的Kp指数。自1977年以来的数据进行了比较，以前公布的日光层电流片测量绘制出的太阳光球。在第21太阳周的下降阶段，雷达后向散射中观察到强周期性行为，但这种周期性在第22太阳周开始时消失。在Kp光谱中，在早期的太阳活动周期中也观察到类似的行为。雷达后向散射，IMF和太阳风光谱的细节表明，太阳风动量密度是决定后向散射周期性的主要参数。两个和四个部门的结构的时间演变，正如SABRE后向散射光谱预测的那样，在整个太阳活动周期21中，通常仍然与日光层电流片测量结果一致。«少
Recurrent variation of geomagnetic activity at the {approximately}27-day solar rotation period and higher harmonics is a well-documented phenomenon. Auroral radar backscatter data from the Sweden and Britain Radar-Auroral Experiment (SABRE) radar provide a continuous time series from 1981 to the present which is a highly sensitive monitor of geomagnetic activity. In this study, Maximum Entropy Method (MEM) dynamic power spectra of SABRE backscatter data from 1981 to 1989, concurrent interplanetary magnetic field (IMF) and solar wind parameters from 1981 to 1987, and the Kp index since 1932 are examined. Data since 1977 are compared with previously published heliospheric current sheet measurements mapped out from the solar photosphere. Stong periodic behavior is observed in the radar backscatter during the declining phase of solar cycle 21, but this periodicity disappears at the start of solar cycle 22. Similar behavior is observed in earlier solar cycles in the Kp spectra. Details of the radar backscatter, IMF, and solar wind spectra indicate that the solar wind momentum density is the dominant parameter in determining the backscatter periodicity. The temporal evolution of two- and four-sector structures, as predicted by SABRE backscatter spectra, throughout solar cycle 21 generally still agree well with heliospheric current sheet measurements.more » For one interval, however, there is evidence that evolution of the current sheet has occurred between the photospheric source surface and the Earth.« less