Virtual Height Variation during Plasma Bubble Evolution Associated with Plasma Blob in Low Latitude Ionosphere
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摘要: 针对东亚地区地磁低纬度南北半球Vanimo台站（地理2.7°S，141.3°E；地磁 11.2°S，146.2°W）和海南台站（地理19.5°N，109.1°E；地磁9.1°N，179.1°W）上空的3个电离层等离子体块与等离子体泡相关联的事件，利用地面台站的电离层测高仪连续观测数据，研究等离子体泡演化期间的电离层虚高变化。结果表明：以往提出的等离子体块出现约2 h之前等离子体垂直漂移速度从向上（东向电场）转为向下（西向电场）的观点，本文的3个事例均与之不符，或者距反转时间很远（约6 h），或者由向下转为向上。在等离子体块形成时间点前的1 h内，均有突发的等离子体堆积的运动趋势，或是下降运动速度突然变慢，或是从下降转为向上运动，或是上升运动速度突然加快。这一堆积现象与等离子体块现象相关性更好，也不仅限于漂移速度从向上转变为向下。Abstract: The observations and theoretical analysis suggest that ionospheric plasma blob could form during the early stage of plasma bubble evolution. In this paper we perform three cases in which ionospheric plasma blob and bubble were associated, to study the virtual height variation during plasma bubble evolution with continuous observations by Digital ionosonde. The cases were over station Vanimo (Geographic 2.7°S, 141.3°E; Geomagnetic 11.2°S, 146.2°W) and Hainan (Geographic 19.5°N, 109.1°E; Geomagnetic 9.1°N, 179.1°W), both in the low latitude region in East Asia sector while in different Hemispheres. The results show that: previous studies suggested that, 2 h before blob occurred, plasma vertical drift velocity would turn from upward (eastward electric field) to downward (westward electric field), but the feature did not show in this study. In our three cases, the turning time was 6 h before blob, or the turning direction was from downward to upward. In addition, 1 h before blob occurred, the ionospheric plasma had sudden compression trend, such as decrease of downward velocity, turn from downward to upward, or increase of upward velocity. This compression was more close to plasma blob, and not limited to the turning of drift direction.
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图 1 2003年6月1日Vanimo台站的观测结果。(a) 电离层F层底部虚高，(b) F层底部垂直运动速度
Figure 1. Observations of Vanimo on 1 June 2003. (a) Virtual height of ionospheric F bottom, (b) vertical drift velocity at F bottom
图 3 2003年10月6日Vanimo台站的观测结果。(a) 电离层F层底部虚高，(b) F层底部垂直运动速度
Figure 3. Observations of Vanimo on 6 October 2003. (a) Virtual height of ionospheric F bottom, (b) vertical drift velocity at F bottom
图 5 2004年3月8日海南台站观测结果。(a) 电离层F层底部虚高，(b) F层底部垂直运动速度
Figure 5. Observations of Hainan on 8 March 2004. (a) Virtual height of ionospheric F bottom, (b) vertical drift velocity at F bottom varied
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