Why are spicules absent over plages and long under coronal holes?
Why are spicules absent over plages and long under coronal holes?
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DOI：
10.1007/bf00151612
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发表时间：
1982-06
期刊：
影响因子：
2.8
通讯作者：
K. Shibata;Y. Suematsu
中科院分区：
文献类型：
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作者：
K. Shibata;Y. Suematsu
为了考察初始大气结构对针状体动力学的影响，进行了一维流体动力学模拟。这是我们之前的针状体理论的扩展版本：针状体是由冲击波（MHD慢模激波）产生的，它起源于光球层或低色球层网络中的亮点外观（突然压力增加）。模拟结果很好地再现了斑上没有针状体和日冕洞下长针状体的观测事实。物理上的原因是激波在色球层传播过程中的增长在斑区很小，在日冕洞区很大，因为激波的增长是由亮点和日冕之间的密度比（ϱh0/ϱc）决定的。得到经验公式ΔHmax ~ （ϱh0/ϱc）0.46，其中ΔHmaxis为过渡区上方针状体的最大高度。在数值模拟中，假设垂直磁通管的截面恒定。
One-dimensional hydrodynamic simulations are performed in order to examine the influence of initial atmospheric structures on the dynamics of spicules. This is an extended version of our previous spicule theory: spicules are produced by the shock wave (MHD slow mode shock) which originates from a bright point appearance (sudden pressure increase) at the network in the photosphere or in the low chromosphere. Simulation results well reproduce the observational facts that spicules are absent over plages and long under coronal holes. The physical reason is that the growth of a shock wave during its propagation through the chromosphere is small in plage regions and large in coronal hole regions, since the growth of a shock is determined by the density ratio (ϱh0/ϱc) between the bright point and the corona. An empirical formula ΔHmax∼ (ϱh0/ϱc)0.46is obtained, where ΔHmaxis the maximum height of spicules above the transition region. The cross-section of the vertical magnetic flux tube is assumed to be constant in the numerical simulations.