First Results from the THEMIS Mission

Angelopoulos, V.; Sibeck, D. G.; Carlson, C. W.; McFadden, J. P.; Larson, D. E.; Lin, R. P.; Bonnell, J. W.; Mozer, F. S.; Ergun, Robert; Cully, C. M.; Glassmeier, K.; Auster, U.; Roux, A.; Contel, O. Le; Frey, S.; Phan, T. D.; Mende, S.; Frey, H. U.; Donovan, E.; Russell, C. T.; Strangeway, R. J.; Liu, J.; Mann, I. R.; Rae, I. J.; Raeder, J.; Li, X.; Liu, W.; Singer, H. J.; Сергеев, В. А.; Apatenkov, S.; Parks, G. K.; Fillingim, M. O.; Sigwarth, J. B.

doi:10.1007/s11214-008-9378-4

Cited by 184 publications

(200 citation statements)

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“…[38] Fast azimuthal plasma flows in the near-Earth plasma sheet have been detected in past studies [e.g., Yeoman et al, 1998;Nakamura et al, 1999;Angelopoulos et al, 2008b]. Using a network of ground magnetometers, Yeoman et al [1998] showed an azimuthal ionospheric feature propagating eastward with a speed of ∼6 km/s that was associated with magnetic dipolarization and fast dawnward plasma flow observed by the Geotail spacecraft located in the near-Earth plasma sheet ∼4 h MLT to the east of the ionospheric disturbances.…”

Section: Discussionmentioning

confidence: 88%

Azimuthal auroral expansion associated with fast flows in the near-Earth plasma sheet: Coordinated observations of the THEMIS all-sky imagers and multiple spacecraft

et al. 2011

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[1] Fast azimuthal auroral expansion and poleward expansion are characteristic features of the expansion phase of substorms. In the first study of its kind, we have investigated the azimuthal auroral expansion and its magnetospheric counterpart using data from Time History of Events and Macroscale Interactions during Substorms (THEMIS) all-sky imagers and multiple spacecraft. During the tail season in 2008-2009, we found 16 events of azimuthally expanding aurora that passed near the magnetic footprints of the multiple spacecraft operating in the near-Earth plasma sheet. In the magnetosphere, these events commonly showed fast azimuthal and earthward flows associated with intense electric fields and magnetic dipolarization. The speed of the propagating structure, which was estimated from the time difference of the depolarization observed by the multiple spacecraft, was close to the measured azimuthal plasma flow velocity. We also found that this azimuthal plasma transport was dominated by the E × B drift speed associated with the enhanced electric field. In a statistical analysis, the averaged speeds of the leading edge of the westward and eastward auroral expansion were 8.8 and 5.3 km/s, respectively. When mapped onto the equatorial magnetosphere, these speeds (267 and 162 km/s) were comparable to the averaged azimuthal plasma (E × B) flow speeds observed by the spacecraft, which were 193 (239) km/s in the westward direction and 112 (139) km/s in the eastward direction. Our events showed that E × B flows and auroral expansion predominantly propagated westward, indicating an effect of westward background convection in the Harang flow shear. From these results, we concluded that the azimuthal auroral expansion was closely related to magnetic dipolarization which expanded azimuthally at the E × B drift speed. On the basis of the abrupt formation of the fast E × B flows and their propagation away from the onset location, we suggest that the effects of the intense large-scale electric fields, which are possibly generated through substorm onset turbulence, propagate to the ionosphere along the magnetic field lines and lead to azimuthal expansion of an auroral arc.

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Section: Discussionmentioning

confidence: 88%

Azimuthal auroral expansion associated with fast flows in the near-Earth plasma sheet: Coordinated observations of the THEMIS all-sky imagers and multiple spacecraft

et al. 2011

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“…The method used in our previous studies has the advantage that it enables us to investigate both temporal and spatial variations in various parameters based on a minimum number of assumptions, and that it offers a perspective view of substorms. Here we focus on both the structure in the X-Z plane and temporal evolution in the equatorial plane using data from the five THEMIS probes (Angelopoulos et al, 2008a) to perform a superposed-epoch analysis. Magnetic-field data and plasma-moment data obtained with the Flux Gate Magnetometer (FGM) (Auster et al, 2008), Electrostatic Analyzer (ESA) and Solid State Telescope (SST) (McFadden et al, 2008) instruments onboard the THEMIS probes (each with 3 s time resolution) are used.…”

Section: Methods Of Analysismentioning

confidence: 99%

Statistical visualization of the Earth's magnetotail and the implied mechanism of substorm triggering based on superposed-epoch analysis of THEMIS data

et al. 2014

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Abstract. To investigate the physical mechanism responsible for substorm triggering, we performed a superposed-epoch analysis using plasma and magnetic-field data from THEMIS probes. Substorm onset timing was determined based on auroral breakups detected by all-sky imagers at the THEMIS ground-based observatories. We found earthward flows associated with north-south auroral streamers during the substorm growth phase. At around X = −12 Earth radii (R E ), the northward magnetic field and its elevation angle decreased markedly approximately 4 min before substorm onset. Moreover, a northward magnetic-field increase associated with pre-onset earthward flows was found at around X = −17 R E . This variation indicates that local dipolarization occurs. Interestingly, in the region earthwards of X = −18 R E , earthward flows in the central plasma sheet (CPS) reduced significantly approximately 3 min before substorm onset, which was followed by a weakening of dawn-/duskward plasma-sheet boundary-layer flows (subject to a 1 min time lag). Subsequently, approximately 1 min before substorm onset, earthward flows in the CPS were enhanced again and at the onset, tailward flows started at around X = −20 R E . Following substorm onset, an increase in the northward magnetic field caused by dipolarization was found in the nearEarth region. Synthesizing these results, we confirm our previous results based on GEOTAIL data, which implied that significant variations start earlier than both current disruption and magnetic reconnection, at approximately 4 min before substorm onset roughly halfway between the two regions of interest; i.e. in the catapult current sheet.

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“…Пять спутников THEMIS (масса одного КА -128 кг) были запущены в 2007 г. [7]. Эти спутники бы-ли реализованы на уже имевшейся у американских коллег малой платформе SMEX и имели на бор-ту достаточно простой набор из пяти стандартных приборов.…”

Section: высокоапогейные спутникиunclassified

Small Satellites for Scientific Research

Petrukovich¹,

Nikiforov²

2016

Rocket-Space Device Engineering and Information Systems

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Аннотация. Рассмотрен мировой опыт запуска научных спутников для исследований плазмы магнитосферы и ионосферы с акцентом на применение малых спутников. Для исследований магнитосферы применяются в основном спутники массой 100-1000 кг. На низкой околоземной орбите (удобной для ионосферных исследований) в последние годы доминируют микро-и наноспутники. В статье представлены перспективные задачи для микро-и наноспутников на различных орбитах, подходы к оценке их эффективности. Обсуждены общие проблемы развития данного направления и возможности их решения в совре-менных условиях как в целом, так и для российского космоса. Abstract. This article reports on the international experience of scientific satellite launches for magnetosphere and ionosphere plasma research with an emphasis on the use of small satellites. For magnetospheric studies, satellites weighting 100-1000 kg are mainly used. In low Earth orbit (convenient for ionospheric studies) micro-and nanosatellites have dominated in the recent years. The paper formulates scientific objectives for the future micro-and nanosatellites in various orbits, as well as approaches to the assessment of their effectiveness. The paper discusses the common problems of this development field and their possible solutions, both as a whole and for the Russian space program in particular.

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First Results from the THEMIS Mission

Cited by 184 publications

References 35 publications

Azimuthal auroral expansion associated with fast flows in the near-Earth plasma sheet: Coordinated observations of the THEMIS all-sky imagers and multiple spacecraft

Azimuthal auroral expansion associated with fast flows in the near-Earth plasma sheet: Coordinated observations of the THEMIS all-sky imagers and multiple spacecraft

Statistical visualization of the Earth's magnetotail and the implied mechanism of substorm triggering based on superposed-epoch analysis of THEMIS data

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