Large-Amplitude ExB Plasma Drifts in the High-Latitude Ionosphere

IF 2.9 2区 地球科学 Q2 ASTRONOMY & ASTROPHYSICS
H. Laakso, R. Pfaff
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Abstract

We investigate the fastest ExB plasma drifts observed by the Vector Electric Field Instrument double probe experiment on the NASA's Dynamics Explorer-2 (DE-2) satellite. In the limited DE-2 database, we find 507 events where the zonal ExB velocity exceeds 4 km/s, in which for 91 events the velocity exceeds 6 km/s and 16 events where the drifts are greater than 8 km/s. One primary group of fast drifts consists of nightside events that occur mostly within the shadowed ionosphere and are related to auroral precipitation (e.g., inverted-V, sub-auroral ion drifts, Alfven waves) driven by magnetospheric processes. Another major group of fast drifts corresponds to dayside events that are often directly driven by the solar wind and can occur within either the sunlit or shadowed ionosphere. The fast drifts are observed at all DE-2 altitudes between 300 and 1,000 km with no altitude dependence on the drift velocity. They are generally observed at all MLT sectors although there appears to be a dawn-dusk asymmetry with the fewest events around 15 MLT. In contrast, the occurrence peaks between 6 and 12 MLT. The events occur in the auroral and sub-auroral altitudes, normally between 60 and 83° of invariant latitude, although in the pre-midnight sector, events are found as low as 50° of invariant latitude, corresponding to sub-auroral ion drift (SAID) events. Surprisingly, with the exception of SAID events, the fast drift events occur during all geomagnetic conditions with the velocities showing no dependence on geomagnetic activity.

Abstract Image

高纬度电离层中的大振幅ExB等离子体漂移
本文研究了美国国家航空航天局(NASA)动力探测器2号(DE-2)卫星上的矢量电场仪双探头实验所观察到的最快的ExB等离子体漂移。在有限的DE-2数据库中,我们发现507个事件纬向ExB速度超过4 km/s,其中91个事件的速度超过6 km/s, 16个事件的漂移大于8 km/s。一组主要的快速漂移由夜侧事件组成,这些事件主要发生在阴影电离层内,并与磁层过程驱动的极光降水(例如,倒v,亚极光离子漂移,阿尔芬波)有关。另一组主要的快速漂移与昼侧事件相对应,这些事件通常直接由太阳风驱动,可能发生在阳光下或阴影下的电离层内。在300至1,000公里之间的所有DE-2高度都观察到快速漂移,与漂移速度无关。它们通常在所有MLT扇区都能观测到,尽管在15mlt附近出现了黎明-黄昏的不对称现象,事件最少。相反,在6和12 MLT之间出现高峰。这些事件发生在极光和亚极光高度,通常在不变纬度的60°至83°之间,尽管在午夜前扇区,事件低至不变纬度的50°,对应于亚极光离子漂移(SAID)事件。令人惊讶的是,除了SAID事件外,快速漂移事件在所有地磁条件下都发生,其速度与地磁活动无关。
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来源期刊
Journal of Geophysical Research: Space Physics
Journal of Geophysical Research: Space Physics Earth and Planetary Sciences-Geophysics
CiteScore
5.30
自引率
35.70%
发文量
570
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