Formation of Heliospheric Arcs of Slow Solar Wind
Formation of Heliospheric Arcs of Slow Solar Wind
复制标题
慢速太阳风日光层弧的形成
DOI：
10.3847/2041-8213/aa6d72
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
T. Zurbuchen
中科院分区：
文献类型：
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作者：
A. Higginson;S. Antiochos;C. DeVore;P. Wyper;T. Zurbuchen
太阳和日光层物理学的一个主要挑战是了解所谓的慢太阳风的起源和性质。太阳的大气层被划分为磁开放区域，称为日冕洞，在那里等离子体自由流出并充满太阳系，以及封闭区域，等离子体被限制在日冕环中。这些区域之间的边界向外延伸的日光层电流片（HCS）。等离子体成分的测量强烈暗示，大部分的慢风由等离子体从封闭的电晕逃逸到开放的场线，大概是由场线开放或交换重连。这两个过程预计将释放封闭场等离子体进入HCS内和紧邻HCS的太阳风。然而，不幸的是，在远离HCS的地方经常观察到具有闭合场等离子体成分的慢风。我们使用高分辨率，三维，磁流体动力学模拟计算的几何形状，包括一个狭窄的走廊两侧封闭的领域，并在冠孔边界的超颗粒状流驱动的冕洞的动态。这些动力学产生了巨大的封闭场等离子弧，这些弧起源于日冕中的开闭边界，但从HCS延伸到很远的地方，在地球上跨越了数十度的纬度和经度。我们的结论是，这种结构可以解释长期令人困惑的慢风观测。
A major challenge in solar and heliospheric physics is understanding the origin and nature of the so-called slow solar wind. The Sun’s atmosphere is divided into magnetically open regions, known as coronal holes, where the plasma streams out freely and fills the solar system, and closed regions, where the plasma is confined to coronal loops. The boundary between these regions extends outward as the heliospheric current sheet (HCS). Measurements of plasma composition strongly imply that much of the slow wind consists of plasma from the closed corona that escapes onto open field lines, presumably by field-line opening or by interchange reconnection. Both of these processes are expected to release closed-field plasma into the solar wind within and immediately adjacent to the HCS. Mysteriously, however, slow wind with closed-field plasma composition is often observed in situ far from the HCS. We use high-resolution, three-dimensional, magnetohydrodynamic simulations to calculate the dynamics of a coronal hole with a geometry that includes a narrow corridor flanked by closed field and is driven by supergranule-like flows at the coronal-hole boundary. These dynamics produce giant arcs of closed-field plasma that originate at the open-closed boundary in the corona, but extend far from the HCS and span tens of degrees in latitude and longitude at Earth. We conclude that such structures can account for the long-puzzling slow-wind observations.