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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Sources of geomagnetic activity over the solar cycle: Relative importance of coronal mass ejections, high-speed streams, and slow solar wind
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Sources of geomagnetic activity over the solar cycle: Relative importance of coronal mass ejections, high-speed streams, and slow solar wind

机译：太阳周期中地磁活动的来源：日冕物质抛射，高速流和缓慢的太阳风的相对重要性

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We assess the contribution of various types of solar wind structures (coronal mass ejections (CMEs), high-speed streams, and slow solar wind) to averages of thf an geomagnetic activity index ((aa)over-bar) during the solar cycle. We used solar wind plasma, magnetic field, and energetic particle data to identify the flow types present in the near-Earth solar wind during 1972-1986 (encompassing the decline of solar cycle 20 and all of cycle 21). Corotating high-speed streams contribute similar to 70% of (aa)over-bar of solar maximum and similar to 30% at solar maximum (1978-1982). CME-related structures (shocks/postshock flows/ejecta) account for similar to 50% of (aa)over-bar at solar maximum and <10% outside of maximum. Slow solar wind contributes similar to 20% throughout the solar cycle. Our analysis provides insight into the Cause of the so-called "Gnevyshev Gap" in geomagnetic activity, characterized by a decrease in (aa)over-bar near the peak of the sunspot cycle. An example of this phenomenon occurred in 1980 at the maximum of cycle 21 when (aa)over-bar registered a value lower than that observed at the preceding solar minimum. We attribute the 1980 depression in an to a temporary reduction in average solar wind speed, evident in both CME and corotating stream related components, and a reduction in mean magnetic fields in all types of solar wind structure. This involvement of all solar wind structures is indicative of a global solar phenomenon, apparently related to an observed depression in tho solar open magnetic flux at the time of solar magnetic field polarity reversal, Both CMEs and streams contribute to geomagnctic activity on either side of this minimum. Thus, at least for cycle 21, the Gnevyshev Gap does not reflect a transition between a period of enhanced geomagnetic activity levels due to CMEs just prior to solar maximum and a second enhancement, due to corotating streams, during the descending phase. Beyond the post Gnevyshev Gap peak, high-speed streams will eventually dominate geomagnetic activity on the decline of the cycle and may, on occasion (as in solar cycle 20), produce a late peak in average geomagnetic activity with relatively little contribution from CMEs. [References: 59]
机译：我们评估了各种类型的太阳风结构（日冕物质抛射（CME），高速流和慢速太阳风）对太阳周期中地磁活动指数（（aa）over-bar）平均值的贡献。我们使用太阳风等离子体，磁场和高能粒子数据来确定1972-1986年近地太阳风中的流类型（包括太阳循环20和整个循环21的下降）。同向旋转的高速流贡献了（aa）太阳最大值（bar）的70％以上，而在太阳最大值（1978-1982）时则贡献了30％。与CME相关的结构（震荡/震后流量/喷出物）在太阳最大时占（aa）越界线的50％左右，而在最大时超出<10％。缓慢的太阳风在整个太阳周期中的贡献率接近20％。我们的分析提供了对地磁活动中所谓“ Gnevyshev差距”成因的认识，其特征是在黑子周期峰值附近的（aa）横线减少。这种现象的一个例子发生在1980年的第21个周期的最大值，当时（aa）跨接记录的值低于在前一个太阳最小值观测到的值。我们将1980年的低迷归因于，平均风速暂时降低，这在CME和与气流同向的相关分量中均显而易见，并且所有类型的太阳风结构中的平均磁场均降低。所有太阳风结构的参与都表明存在全球性太阳现象，这显然与太阳磁场极性反转时观测到的太阳开放磁通量下降有关。最低。因此，至少对于周期21而言，格涅维雪夫峡没有反映出由于地磁活动水平正好在太阳最大之前而导致的地磁活动水平增强与下降阶段由于同向流引起的第二次增强之间的过渡。除了Gnevyshev峡峰之后的峰值外，随着周期的下降，高速流最终将主导地磁活动，有时（如太阳周期20）可能会产生平均地磁活动的后期峰值，而CME的贡献相对较小。 [参考：59]

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