慢太阳风中的小冕洞风和阿尔芬波

The small coronal hole solar wind and Alfvén wave within the slow solar wind

慢太阳风的起源是一个困扰空间物理领域多年的问题,一些研究人员认为慢太阳风中阿尔芬度比较高的部分起源于小冕洞或者是冕洞的边界,不过另外一些研究者发现高阿尔芬度慢太阳风在成分上和低阿尔芬度的慢太阳风并无显著差别.最近的一项研究中发现的慢太阳风中的小冕洞风并没有特别高的阿尔芬度.我们利用一个简单的二维太阳风模型计算了阿尔芬波和小冕洞风的传播;计算结果显示,由于阿尔芬波的传播特性,从小冕洞出发的等离子体和阿尔芬波动在传播到1AU的过程中会发生分离,形成了低阿尔芬度的小冕洞风和高阿尔芬度的普通慢风.这个结果定性地解释了慢太阳风中观测到的小冕洞风和高阿尔芬度慢风的特性,也为解开慢太阳风的起源之谜提供了新的思路.

The origin of the slow solar wind has been a puzzle in the field of space physics for many years.Some researchers suggest that Alfvénic slow winds originate from small coronal holes or at the boundary of coronal holes,although others have found that Alfvénic slow winds does not differ in compositions from the non-Alfvénic slow wind.A small coronal hole wind embedded in the slow solar wind is reported recently,but of lower Alfvénicity.We calculated the propagation of small coronal hole winds and Alfvén waves using a simple two-dimensional solar wind model;the results show that the Alfvén waves are separated from the co-originated plasma during the propagation,leading to small coronal hole winds with low Alfvénicity and ordinary slow winds with high Alfvénicity.This result qualitatively explains the properties of the small coronal hole winds and Alfvénic slow wind with normal slow wind properties.This study provides a new insight into the origin of the slow solar wind mystery.