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Cluster observations of high-altitude cusp during multiple fast-turning ImF

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Chinese Science Bulletin 2010年第22期55卷 1178-1185页

作者： CAI HongTao mA ShuYing dunlop m w BOGDANOVA Y DAVIES J A PITOUT F School of Electronic Information Wuhan University Wuhan 430079 China Key Lab of Geospace Environment and Geodesy CNEM Wuhan 430079 China SSTD Rutherford Appleton Laboratory Chilton OX11 OQX UK Department of Physics La Trobe University Melbourne Victoria 3086 Australia max-Planck-lnstitut fiir Extraterrestrische Physik Garching D-37191 Germany

Using coordinated observations from the Cluster,DmSP and ESR radar,high-altitude cusp was investigated for a time period characterized by four fast reversals of the ImF *** February 12,2003,Cluster was flying sunward at duskside over the Northern Hemisphere,across the high-altitude northern cusp *** the two crossings are during steady northward ImF interval,whereas ion fluxes detected during the time period are quite *** cusp in the first crossing is a "typical" northward-ImF one,with short-lived ion injections of evident "reversed" dispersion *** the second crossing,however,the cusp appears to be a region reminiscent of the Stagnant Exterior Cusp (SEC).In addition,evident upward-flowing O+ ion bursts,possibly original from polar ionosphere,are also detected during the second cusp crossing,together with enhancement of trapped magnetospheric-like electron *** suggest that the SEC-like cusp is likely on newly closed field lines,which were first reconnected (being opened) at low latitudes and later reconnected again (being closed) poleward of the northern cusp.

关键词：国际货币基金组织高海拔群集观测十字路口离子检测低纬度地区气象卫星

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Near Earth Vortices Driving of Field Aligned Currents Based on magnetosphere multiscale and Swarm Observations

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空间科学学报 2019年第1期39卷 9-17页

作者： ZHANG C SHEN C YANG Y Y dunlop m w TI S RUSSELL C T LüHR H BURCH J L LINDQVIST P A TORBERT R B FRIIS-CHRISTENSEN E State Key Laboratory of Space weather National Space Science Center College of Earth Science University of Chinese Academy of Sciences College of Science Harbin Institute of Technology Institute of China Seismological Bureau Crustal Stress Space Science Institute School of Astronautics Beihang University Rutherford Appleton Laboratory University of California German Research Center For Geosciences German Research Center for Geosciences Southwest Research Institute Royal Institute of Technology University of New Hampshire Danish National Space Center

A long-standing mystery in the study of Field-Aligned Currents(FACs) has been that: how the currents are generated and why they appear to be much stronger at high altitudes than in the ionosphere. Here we present two events of magnetotail FACs observed by the magnetospheric multiscale Spacecraft(mmS) on 1 st July and 14 th July 2016, to show how the Substorm Current wedges(SCw) were formed. The results show that particles were transferred heading towards the Earth during the expansion phase of *** azimuthal flow formed clockwise(counter-clockwise) vortex-like motion, and then generated downward(upward) FACs on the tailward/poleward side of the distorted field with opposite vorticity on their Earthward/equatorward side. we also analyzed the Region 1 FACs observed by the Earth Explorer Swarm spacecraft on 1 st July 2016 and found that they were associated with FACs observed by mmS, although differing by a factor of 10. This difference suggests that either there was the closure of the currents at altitudes above 500 km or the currents were not strictly parallel to B and closed at longitudes away from where they were generated.

关键词： Substorm current wedge magnetosphere Field-aligned currents Flow vorticity multiple spacecraft measurements

2004年3月13日TC-1和Cluster卫星联合观测的磁通量传输事件

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空间科学学报 2009年第2期29卷 166-174页

作者：张清和刘瑞源黄际英 dunlop m w 胡红桥胡泽骏 Bogdanova Y V walsh A 西安电子科技大学理学院西安710071 中国极地研究中心 Space Science Department Rutherford-Appleton LaboratoryChiltonDidcotUK mullard Space Science Laboratory University College LondonDorkingSurreyUK

分析了2004年3月13日12:15到12:25UT期间TC-1和Cluster卫星簇的磁通门磁力计(FGm)和电子/电流试验仪(PEACE)的联合观测数据.在此期间,TC-1卫星位于日下点以南的磁层顶附近的磁鞘中,并在12:19UT左右观测到了一个典型的先正后负的磁鞘磁... 详细信息

分析了2004年3月13日12:15到12:25UT期间TC-1和Cluster卫星簇的磁通门磁力计(FGm)和电子/电流试验仪(PEACE)的联合观测数据.在此期间,TC-1卫星位于日下点以南的磁层顶附近的磁鞘中,并在12:19UT左右观测到了一个典型的先正后负的磁鞘磁通量传输事件(FTE);向Cluster卫星簇位于北半球日侧高纬磁层顶附近,并于12:23UT左右穿出磁层顶进入磁鞘,且在12:21UT左右也观测到了一个典型的先正后负的磁层FTE.比较分析发现此两个FTE具有类似的磁场结构和等离子体特征,可能是同一个北向运动的FTE先后被TC-1和Cluster卫星观测到.利用Cluster 4颗卫星的多点同时观测数据,采用最小方向微分法和时空微分方法,推断Cluster卫星观测的这个FTE是尺度大小约为1.21 R_e的准二维结构,其运动方向为东北方向,与Cooling模型预测方向基本一致.利用Cooling模型的预测,推算了TC-1卫星在12:19UT观测的FTE的运动速度和尺度,进而得出随着通量管的极向运动,其速度和尺度均有所增加.

关键词：磁重联 FTE Cooling模型 Cluster

A new processing method for the AE index

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Science China(Technological Sciences) 2008年第10期51卷 1713-1720页

作者： w. BAUmJOHANN m. dunlop Space Research Institute Austrian Academy of Sciences Graz Austria Space Sciences Division Rutherford Appleton Laboratory Chilton Didcot United Kingdom

In this paper, we introduce an effective processing method to acquire the time de-rivative of the AE index as a coefficient. Using this coefficient, the AE index can be divided into the four stages: quiet, ascending, descending and active stages. The statistical results show that the ascending and descending stages of the AE index are dominant and occupy two thirds of the whole period. An analysis of the rela-tionship between the occurrence frequencies of the Dst index and AE index in solar cycle 23 shows that the monthly variation of the occurrence frequencies of the ascending stage of AE is closely related to the decrease of the Dst index.

关键词： AE index Dst index FIR filter substorm

Relationship between FAC at plasma sheet boundary layers and AE index during storms from August to October,2001

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Science China(Technological Sciences) 2008年第7期51卷 842-848页

作者： dunlop m Imperial College London London SW7 2AZ UK

Unlike the previous single (dual) satellite observation, the four Clusterll satellites make it possible to directly compute the continuous field-aligned current (FAC) density according to the magnetic data from them and to enable the investigation of the relationship between the FAC and geomagnetic activity. This paper analyzes the observation data when the Cluster satellites crossed the plasma sheet boundary layer (PSBL) in the magnetotail during the two magnetic storms in August to October 2001. According to the data, during the magnetic storms the relationship between the variations of FAC and AE index turned out to be: 1) FAC was obviously increasing during the storms; 2) FAC density was approximately negatively correlated with AE index from the sudden commencement to the early main phase of the storm; 3) they were approximately positively correlated during the late main phase and early recovery phase; 4) they were no apparent correlation during the late recovery phase.

关键词： ionosphere-magnetosphere storm cases FAC AE index

Near-Earth bursty bulk flows and AE index

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Science China(Technological Sciences) 2008年第10期51卷 1704-1712页

作者： w BAUmJOHANN m. w. dunlop C. CARR H. RmE Space Research Institute Austrian Academy of Sciences Graz Austria Space Sciences Division Rutherford Appleton Laboratory Chilton Didcot UK Imperial College London United Kingdom Centre d'Etude Spatiale des Rayonnements Toulouse France

with the 4-s resolution data of the magnetometer and the ion plasma analyzer on TC-1 from June to November of each year during the period of 2004―2006, we statistically analyzed the occurrence rate of both convective and field-aligned bursty flows (FABFs). A near-Earth bursty bulk flow (NEBBF) occurred during both the quiet time and substorm process. In general, the magnetic field and the plasma density began oscillating with the appearance of the NEBBF associated with a distinct increase of the AE index. The increase of AE index during the NEBBF was more than 100 nT in both quiet time and substorm process. The statistical analysis indicated that the occurrence rates of the FABFs were nearly the same in the dif-ferent stages of the AE index, but the occurrence rate of the NEBBFs was much higher in the growth stage of the AE index, indicating that the NEBBFs were di-rectly related to the growth and expansion phases of the substorm. The observa-tions suggested that the quite large number of BBFs from the mid magnetotail could enter into the near-Earth tail and play important role in triggering the sub-storm onset.

关键词： BBF near-Earth AE index substorm onset

The radial evolution of earthward BBFs during substorm

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Science China Earth Sciences 2010年第10期53卷 1542-1551页

作者： REmE H DANDOURAS I LUCEK E dunlop m Centre d'Etude Spatiale des Rayonnements Blackett Laboratory Imperial College London Rutherford Appleton Laboratory

we here study the occurrence rate,probability function of velocity and duration of earthward bursty bulk flows(BBFs) in the Inner Plasma Sheet(IPS,β>0.5) using the data of Cluster in 2001 and *** occurrence rate of earthward BBFs increases with distance from the Earth up to ?19 RE,which is in agreement with the previous observations of the radial evolution of *** 54% of earthward BBFs in expansion phase have a velocity larger than 600 km/s,whereas only 38% of earthward BBFs in growth and recovery phases have a velocity larger than 600 km/*** average velocity of earthward BBFs in expansion phase is 732 km/s,larger than those in growth phase(631 km/s) and recovery phase(617 km/s).The durations of earthward BBFs decrease with the decrease of downtail distance from Earth due to the braking of earthward *** duration of earthward BBFs in expansion phase is larger than that in growth and recovery *** average durations in growth,expansion,and recovery phases are respectively 49.3,71.5,and 47.6 ***,the ratios of transports of energy of earthward BBFs in growth,expansion,and recovery phases can be estimated to be 0.51:1:***,the earthward BBFs in the expansion phase have the largest capability of the transport of energy and can produce the largest braking effects,such as inertial currents and auroral activities.

关键词： substorm growth expansion recovery duration energy transport

magnetospheric Boundary Layer Structure and Dynamics as Seen From Cluster and Double Star measurements

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空间科学学报 2013年第6期33卷 577-603页

作者： Y V Bogdanova C J Owen m w dunlop m G G T Taylor A N Fazakerley Space Science and Technology Department RALChiltonDidcotOxfordshireOX11 0QXUK mullard Space Science Laboratory University College LondonHolmbury St.MaryDorkingSurreyRH5 6NTUK Science and Robotic Exploration Directorate ESA/ESTECNoordwijkThe Netherlands

In this review,we discuss the structure and dynamics of the magnetospheric LowLatitude Boundary Layer(LLBL)based on recent results from multi-satellite missions Cluster and Double *** boundary layer,adjacent to the magnetopause on the magnetospheric side,usually consists of a mixture of plasma of magnetospheric and magnetosheath origins,and plays an important role in the transfer of mass and energy from the solar wind into the magnetosphere and subsequent magnetospheric *** southward Interplanetary magnetic Field(ImF)conditions,this boundary layer is generally considered to be formed as a result of the reconnection process between the ImF and magnetospheric magnetic field lines at the dayside magnetopause,and the structure and plasma properties inside the LLBL can be understood in terms of the time history since the reconnection *** northward ImF conditions,the LLBL is usually thicker,and has more complex structure and *** observations confirm that the LLBL observed at the dayside can be formed by single lobe reconnection,dual lobe reconnection,or by sequential dual lobe reconnection,as well as partially by localized cross-field *** LLBL magnetic topology and plasma signatures inside the different sub-layers formed by these processes are discussed in this *** role of the Kelvin-Helmholtz instability in the formation of the LLBL at the flank magnetopause is also ***,we conclude that the LLBL observed at the flanks can be formed by the combination of processes,(dual)lobe reconnection and plasma mixing due to non-linear Kelvin-Helmholtz waves.

关键词：边界层结构磁层顶双星群集国际货币基金组织等离子体特性测量拓扑结构

Solar wind transport into magnetosphere caused by magnetic reconnection at high latitude magnetopause during northward ImF: Cluster-DSP conjunction observations

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Science China(Technological Sciences) 2008年第10期51卷 1677-1684页

作者： m. dunlop E. LUCEK H. RmE C. m. CARR Rutherford Appleton Laboratory Didcot United Kingdom Imperial College of Science Technology and Medicine London United Kingdom CESR BP4346 31028 Toulouse Cedex 4 France

An event of Cluster-Double Star conjunction observations of magnetic reconnec-tion at high latitude magnetopause nightside of both cusps and solar wind trans-port into magnetosphere caused by such reconnection process has been investi-gated. During northward ImF, Cluster/SC1 observed accelerated flows and ion heating associated with magnetic reconnection at high latitude magnetopause nightside of southern cusp. And Double Star observed cold dense solar wind plasma transported into dayside magnetosphere. The analysis on such conjunction observations shows that: (1) during northward ImF, magnetic reconnection occurs at high latitude nightside of southern cusp, accompanied by accelerated flows that are observed by Cluster/SC1; (2) the direction of the accelerated flows, with its sunward component Vx, dawnward component Vy, northward component Vz, is quite consistent with the theoretical anticipation under the condition of northward ImF with dawnward component By; (3) reconnection can heat plasma more in par-allel direction than in perpendicular direction, to a level of about 4 keV; (4) with reconnection taking place at high latitude magnetopause nightside of the southern cusp, TC-1 observed cold and dense plasma transported into magnetosphere; (5) by reconnection at high latitude magnetopause nightside of both cusps, solar wind flux tube can be captured by magnetosphere and pulled into dayside magneto-sphere. This event presents further observational evidence for magnetic reconnec-tion at high latitude magnetopause nightside of both cusps as an important mech-anism of sol-ar w-ind transport into magnetosphere.

关键词： transport process magnetic reconnection solar wind-magnetosphere interactions