Solar Cycle Variation of Magnetic Flux Ropes in a Quasi-Static Coronal Evolution Model
Solar Cycle Variation of Magnetic Flux Ropes in a Quasi-Static Coronal Evolution Model
复制标题
准静态日冕演化模型中磁通量绳的太阳周期变化
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
P. Martens
中科院分区：
文献类型：
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作者：
A. Yeates;J. Constable;P. Martens
日冕中的电流结构和磁螺旋度与11年周期的太阳活动密切相关，但人们对此知之甚少。作为一种替代传统的无电流的“势场”外推，我们调查的全球日冕磁场的模型，这是非潜在的和时间依赖性的，以下的建立和运输的磁螺旋度由于磁通量出现和大规模的光球运动。这种螺旋性集中成扭曲的磁通量绳，可能会失去平衡并被弹出。在这里，我们考虑这个模型预测的磁结构-特别是通量绳-在太阳活动周期的变化，根据光球输入数据从周期23的六个时期。通量绳的数量从最小值到最大值增加一倍，遵循光球极性反转线的总长度。然而，磁绳喷射的数量增加了八倍，以下活跃地区的出现率。这与观测到的日冕物质抛射的周期调制大致一致，尽管模拟中的实际抛射率约为观测事件率的五分之一。该模型预测，即使在最低限度，差异旋转将产生剪切，非潜在的，在所有纬度的磁结构。
The structure of electric current and magnetic helicity in the solar corona is closely linked to solar activity over the 11-year cycle, yet is poorly understood. As an alternative to traditional current-free “potential-field” extrapolations, we investigate a model for the global coronal magnetic field which is non-potential and time-dependent, following the build-up and transport of magnetic helicity due to flux emergence and large-scale photospheric motions. This helicity concentrates into twisted magnetic flux ropes, which may lose equilibrium and be ejected. Here, we consider how the magnetic structure predicted by this model – in particular the flux ropes – varies over the solar activity cycle, based on photospheric input data from six periods of cycle 23. The number of flux ropes doubles from minimum to maximum, following the total length of photospheric polarity inversion lines. However, the number of flux rope ejections increases by a factor of eight, following the emergence rate of active regions. This is broadly consistent with the observed cycle modulation of coronal mass ejections, although the actual rate of ejections in the simulation is about a fifth of the rate of observed events. The model predicts that, even at minimum, differential rotation will produce sheared, non-potential, magnetic structure at all latitudes.