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首页> 外文期刊>The Astrophysical journal >MAGNETIC FIELD CONFINEMENT IN THE CORONA: THE ROLE OF MAGNETIC HELICITY ACCUMULATION
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MAGNETIC FIELD CONFINEMENT IN THE CORONA: THE ROLE OF MAGNETIC HELICITY ACCUMULATION

机译：日冕中的磁场限制：磁螺旋堆积的作用

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摘要

A loss of magnetic field confinement is believed to be the cause of coronal mass ejections (CMEs), a major form of solar activity in the corona. The mechanisms for magnetic energy storage are crucial in understanding how a field may possess enough free energy to overcome the Aly limit and open up. Previously, we have pointed out that the accumulation of magnetic helicity in the corona plays a significant role in storing magnetic energy. In this paper, we investigate another hydromagnetic consequence of magnetic-helicity accumulation. We propose a conjecture that there is an upper bound on the total magnetic helicity that a force-free field can contain. This is directly related to the hydromagnetic property that force-free fields in unbounded space have to be self-confining. Although a mathematical proof of this conjecture for any field configuration is formidable, its plausibility can be demonstrated with the properties of several families of power-law, axisymmetric force-free fields. We put forth mathematical evidence, as well as numerical, indicating that an upper bound on the magnetic helicity may exist for such fields. Thus, the accumulation of magnetic helicity in excess of this upper bound would initiate a nonequilibrium situation, resulting in a CME expulsion as a natural product of coronal evolution.
机译：磁场限制的损失被认为是日冕物质抛射（CME）的原因，日冕物质抛射是日冕中太阳活动的主要形式。磁能存储的机制对于理解磁场如何拥有足够的自由能来克服Aly极限并开放至关重要。先前，我们已经指出电晕中磁螺旋的积累在存储磁能中起着重要作用。在本文中，我们研究了磁螺旋堆积的另一个水磁结果。我们提出一个推测，即无力场可以包含的总磁螺旋度有一个上限。这直接与水磁特性有关，即无界空间中的无力场必须是自约束的。尽管对任何场配置的这种猜想都有数学上的证明，但它的合理性可以通过数个幂律，无轴对称力场的性质来证明。我们提出了数学证据以及数值证据，表明此类磁场可能存在磁螺旋的上限。因此，超过该上限的磁性螺旋的积累将引发不平衡的情况，导致CME排出作为日冕演化的天然产物。

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