TWO EVENTS SHOWING THE INTERACTION OF INTENSE MAGNETIC CLOUD WITH COROTATING HIGH SPEED STREAMS
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摘要: 本文利用行星际观测数据, 分析了1978年8、9月间同一起源的共转高速流两次与磁云发生的相互作用.8月27日, 强磁云为共转高速流所追赶, 磁云前半部为磁云本体, 具有强磁云的基本特征, 但后半部则为高速流追赶磁云的相互作用区, 流速图象具有明显的双台阶特征.9月25日另一异常强磁云追赶再次重现的共转高速流, 磁云前部为相互作用区, 后部为磁云本体, 但结构特征较简单磁云复杂;磁云前部流速峰值超过900km/s, 而在磁云本体.Alfvén波速峰值在600km/s以上, 非常接近局部太阳风速.此两事例进一步说明了Alfvén波速增强对磁云加速的重要作用.此外, 还就磁云引起的磁暴和宇宙线下降的特性进行了讨论.Abstract: Two intese magnetic clouds interacted with same corotating high-speed solar wind stream recurring in two successive rotations during the fall of 1978. For the August 27, 1978 event, an intense magnetic cloud was overtaken by a corotating high speed stream, the first half of the cloud can be identified with the cloud body that still retains the basic properties of a simple intense cloud; while the second half is the interaction region resulted from the overtaking magnetic cloud by the high speed stream, the speed profile of which displays a two-steps feature. For the September 25, event, another extraordinary intense magnetic cloud was overtaking the corotating high speed stream recurring again, the first half of the cloud can be identified with an interaction region; while the second half is the cloud body itself with a rather complex structure than the simple cloud without interactions. In the second case, the bulk velocity reached a very high peak value greater than 900km/s in the interaction region, also the Alvenic speed a very high value above 600 km/s in the cloud body which was very close to the local solar wind speed. These two events discussed in this paper show further the important role played by an enhancement of the Alfvenic speed in accelerating the magnetic cloud. The properties of the geomagnetic storm and the cosmic ray decrease caused by the clouds are also briefly discussed in association with the Kp category of geomagnetic storm proposed by he author.
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