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学术报告:Plasma Sheet O+ concentration impacts on the sawtooth/substorm events

(2013-04-09)
时间:4月11日(周四)下午3点
地点:行政科研楼1514会议室
报告人:廖静  (博士)
单位:新罕布什尔大学
摘要:In order to study the relationship between sawtooth events and the plasma composition of the plasmasheet, we perform a detailed superposed epoch study of O+ concentration inside the near-Earth plasmasheet during sawtooth events and substorms sorted by different geomagnetic storm phases, using Cluster/CODIF data. The statistical results show that the O+ content increases during the sawtooth growth phase, regardless of the storm phase, reaches 20% around the dipolarization. During storm main phase, the plasma sheet O+ concentration during sawtooth events is only slightly higher than that observed during storm time substorm events. However, during storm recovery phase and non-storm times, there is significantly more O+ within the plasma sheet during sawtooth events than during storm time substorm events. No difference is found in the comparison between the O+/H+ density ratio changes during the first tooth in a series of sawtooth and the subsequent teeth. Hence, there is no evidence to support the hypothesis that subsequent teeth will lead to a closer near-Earth X-line due to the higher O+ inside the plasma sheet. Finally, despite the association between sawtooth events and high O+/H+ ratio, there are times when the O+/H+ density ratio is high in the plasma sheet but no sawtooth event is observed, and there are sawtooth events when the O+/H+ ratio is low.  This indicates that enhanced O+ is likely one of many factors that play a role in triggering the sawtooth events.

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