Statistical analysis of long-duration low-density solar wind events
Statistical analysis of long-duration low-density solar wind events
复制标题
长持续时间低密度太阳风事件统计分析
DOI：
10.5194/angeo-19-17-2001
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发表时间：
2001
影响因子：
1.9
通讯作者：
K. Marubashi
中科院分区：
文献类型：
--
作者：
S. Watari;Takashi Watanabe;K. Marubashi
抽象的。1999年5月11日至12日，通过现场观测，观测到了持续时间较长的低太阳风密度。作为这种低密度太阳风条件的结果，地球的磁层显著扩大。我们使用了一个接近1AU的一小时平均太阳风(1963-1999)的数据库来确定所观测到的低密度事件是否非常异常。结果发现，在大约36年的太阳风观测中，这一事件的持续时间最长。密度在0.5厘米~(-3)或以下，持续时间在10小时或更长的有三次。分别于1979年7月4日和31日以及1999年5月11日至12日进行了观察。1979年7月4日事件于1979年7月31日再次发生。这些事件的特点是低贝塔、低阿尔芬马赫数(MA)和低动态压力。密度在0.5 cm~(-3)以下的低密度太阳风的出现率在太阳极大值附近出现多个峰值。然而，太阳黑子数量和出现率之间很难找到明确的关系。关键词。行星际物理学(耀斑和流动力学；太阳风等离子体；太阳风的来源)
Abstract. Low solar wind density with long duration was measured by in situ observation between 11 and 12 May 1999. As a result of this low-density solar wind condition, the magnetosphere of the Earth expanded considerably. We used a database of one-hour-averaged solar wind (1963–1999) near 1 AU to determine whether or not the observed low-density event was extremely abnormal. As a result it was found that this event has the longest duration in approximately 36 years of solar wind observations. There are three events with density 0.5 cm -3 or less and duration ten hours or longer. They were observed on 4 and 31 July 1979, and 11–12 May 1999. The 4 July 1979 event recurred on 31 July 1979. The events were characterized by low-beta, low Alfven Mach number ( M A ), and low dynamic pressure. The occurrence rate of low-density solar wind with density 0.5 cm -3 or less shows several peaks near solar maxima. However, it is difficult to find a clear relationship between the sunspot number and the occurrence rate. Key words. Interplanetary physics (flare and stream dynamics; solar wind plasma; sources of the solar wind)