A Floor in the Solar Wind Magnetic Field

A Floor in the Solar Wind Magnetic Field
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太阳风磁场中的一层

DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
E. Cliver
E. Cliver
中科院分区：
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文献类型：
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作者：
L. Svalgaard;E. Cliver

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根据地磁指数对行星际磁场（IMF）进行的长期（~130年）重建表明，太阳风磁场强度有一个“底”，这是一个年平均基线值，在每11年的太阳活动最小值时接近。在黄道平面1 Au，IMF地板是~4.6 nT，直接太阳风测量和宇宙起源核数据证实的值。在高日纬度下，在1995年太阳极小期观测到的太阳极场为~100 μT，2006年观测到的太阳极场为~60 μ T，以及2001年太阳极大期观测到的太阳极场接近于零时，地球物理学家测量到一个恒定的径向场，其大小（归一化为1 Au）为~3.2 nT。我们确定地板与恒定的（几个世纪以来）基线开放磁通量在1 Au的~4 × 1014 Wb，对应于恒定强度（~1011 A）的日光层电流。IMF强度的太阳周期变化骑在地板上。这一层对（1）大极小期的太阳风--我们每隔11年就能看到蒙德极小期的太阳风--（2）目前的太阳风模型--无论是源面模型还是MHD模型都是建立在最大尺度场决定IMF大小的假设基础上的，这一假设已被Einstein证明是无效的，因此，这些模型不能再现高纬度的观测结果;以及（3）使用地磁输入数据对即将到来的太阳黑子极大期进行预测--由于观测到的太阳极场强度和日光层场强度之间的脱节，这种常见的做法令人怀疑。
Long-term (~130 years) reconstruction of the interplanetary magnetic field (IMF) based on geomagnetic indices indicates that the solar wind magnetic field strength has a "floor," a baseline value in annual averages that it approaches at each 11 yr solar minimum. In the ecliptic plane at 1 AU, the IMF floor is ~4.6 nT, a value substantiated by direct solar wind measurements and cosmogenic nuclei data. At high heliolatitudes, Ulysses measured a constant radial field with a magnitude (normalized to 1 AU) of ~3.2 nT during solar minimum conditions in ~1995 when the observed solar polar fields were ~100 μT and in 2006 when the polar fields were ~60 μT, as well as for solar maximum conditions in 2001 when the polar fields were close to zero. We identify the floor with a constant (over centuries) baseline open magnetic flux at 1 AU of ~4 × 1014 Wb, corresponding to a constant strength (~1011 A) of the heliospheric current. Solar cycle variations of the IMF strength ride on top of the floor. The floor has implications for (1) the solar wind during grand minima—we are given a glimpse of Maunder minimum conditions at every 11 yr minimum; (2) current models of the solar wind—both source surface and MHD models are based on the assumption, invalidated by Ulysses, that the largest scale fields determine the magnitude of the IMF; consequently, these models are unable to reproduce the high-latitude observations; and (3) the use of geomagnetic input data for precursor-type predictions of the coming sunspot maximum—this common practice is rendered doubtful by the observed disconnect between solar polar field strength and heliospheric field strength.