The THEMIS all-sky imaging array -: system design and initial results from the prototype imager
The THEMIS all-sky imaging array -: system design and initial results from the prototype imager
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DOI：
10.1016/j.jastp.2005.03.027
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发表时间：
2006-09-01
影响因子：
1.9
通讯作者：
Connors, Martin
中科院分区：
文献类型：
--
作者：
Donovan, Eric;Mende, Stephen;Connors, Martin
亚暴期间事件和大尺度相互作用的时间历史(THEMIS)是NASA MIDEX计划于2006年发射的一项任务。THEMIS将由赤道轨道上的五颗磁层卫星组成。其中三个航天器的远地点将在12Re左右，而第四个和第五个航天器的远地点将在类似20和类似30 Re的位置。12、20和30个远地点轨道将分别有1、2和4个恒星日的周期，这意味着所有五个航天器将每四个恒星日在同一子午线上处于或接近远地点。此外，在整个任务期间，这些会合将始终发生在加拿大中部。这五颗THEMIS卫星将配备粒子和场探测器，用于测量中央等离子体片(CPS)中的相关等离子体参数、场和整体速度。THEMIS星座将包括电流中断(CD)和近地中性线(NENL)区域，并将首次提供明确识别亚暴过程启动的CPS中的径向位置的机会。THEMIS的主要科学目标是确定这些过程中的哪一个是引发亚暴的原因。如果不在北美进行补充的地面观测，Themis就无法解决这个问题。为此，THEMIS需要在整个大陆的阵列中部署20个白光全天成像仪(ASIS)。这些ASIS将以每5张S至少一张图像的节奏运行，并将提供关键任务开始和早期扩张阶段的信息。在这篇文章中，我们提供了一个亚暴事件的原型THEMIS ASI的观测结果。这一图像数据表明，THEMIS ASI具有满足任务要求所需的时间和空间分辨率。此外，在这种情况下，我们发现生长相弧显示出波浪状的方位结构和几乎同时发生的沿ASI视场内的整个弧长的增亮。我们将这种波状结构归因于CPS中的结构。我们预计，THEMIS ASI阵列和现场数据将有助于阐明产生这种方位结构的CPS过程。(C)2006年，爱思唯尔有限公司出版。
Time History of Events and Macroscale Interactions during Substorms (THEMIS) is a NASA MIDEX mission scheduled for launch in 2006. THEMIS will consist of five magnetospheric satellites in equatorial orbits. Three of the spacecraft will have apogees around 12 Re, while the fourth and fifth will have apogees at similar to 20 and similar to 30 Re. The 12, 20, and 30 Re apogee orbits will have periods of one, two, and four sidereal days, respectively, meaning that all five spacecraft will be at or near apogee in the same meridian every four sidereal days. Furthermore, these conjunctions will always occur over central Canada throughout the mission duration. The five THEMIS satellites will be instrumented with particle and field detectors for measuring relevant plasma parameters, fields, and bulk velocities in the central plasma sheet (CPS). The THEMIS constellation will bracket the current disruption (CD) and near-earth neutral line (NENL) regions and will provide for the first time an opportunity for unambiguous identification of the radial position in the CPS where the substorm process initiates. The primary scientific objective for THEMIS is to determine which of these processes is responsible for substorm onset. THEMIS cannot close this question without complementary ground-based observations in North America. To this end, THEMIS requires the deployment of 20 white light all-sky imagers (ASIs) in a continent-wide array. These ASIs will operate with a cadence of at least one image every 5 s, and will provide mission critical onset and early expansive phase information. In this paper, we present observations from the prototype THEMIS ASI for one substorm event. This image data demonstrates that the THEMIS ASI has the temporal and spatial resolution necessary to meet the mission requirements. Further, in this event we find that the growth phase arc shows wavelike azimuthal structuring and a brightening that occurs virtually simultaneously along the entire length of the arc that is within the ASI field of view. We attribute this wavelike structure to structure in the CPS. We anticipate that the THEMIS ASI array and in situ data will allow for the elucidation of the CPS process that generates this azimuthal structure. (C) 2006 Published by Elsevier Ltd.