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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, A07S01, doi:10.1029/2008JA013146, 2008

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Introduction to special section on Double Star-Cluster Coordinated Studies on Magnetospheric Dynamic Processes Q.-G. Zong,1,2 C. P. Escoubet,3 Z. Y. Pu,1 and Z. X. Liu4 Received 4 March 2008; revised 29 April 2008; accepted 7 May 2008; published 30 July 2008.

Citation: Zong, Q.-G., C. P. Escoubet, Z. Y. Pu, and Z. X. Liu (2008), Introduction to special section on Double Star-Cluster Coordinated Studies on Magnetospheric Dynamic Processes, J. Geophys. Res., 113, A07S01, doi:10.1029/2008JA013146.

1. Introduction [1] The Double Star Program (DSP) is not only the first Chinese scientific satellite program but also the first collaborative mission between the China National Space Administration (CNSA) and the European Space Agency (ESA) [Liu et al., 2005]. This mission consists of two spacecraft, designed to investigate magnetospheric, global dynamic processes, and their response to solar wind-forcing and interplanetary magnetic field (IMF) disturbances, in conjunction with the previously launched four-satellite ESA Cluster Mission (Figure 1). The first spacecraft of DSP, called in Chinese ‘‘Tan Ce – 1’’ (TC-1 – Explorer-1), was launched successfully by a Chinese Long March 2C rocket at 2006 CET on 29 December 2003, into an elliptical orbit with perigee height of 550 km and apogee of 66,970 km, and inclined at 28.5 degrees to the equator (orbital period 27.4 h). TC-2 was launched also by a Chinese Long March 2C rocket at 1515 CET on 25 July 2004 into a polar orbit, having a perigee height of 700 km and apogee height of 39,000 km, with a period of 11.7 h. [2] The orbits of the two Double Star spacecraft have been specially designed to complement the ESA Cluster mission by maximizing the time periods when both Cluster and Double Star are in the same magnetospheric regions or connected magnetically with each other. The two missions together allow simultaneous observations of the Earth magnetosphere from six points in space in a three-dimensional manner. Together with the four Cluster spacecraft, on the dayside, the TC-1 orbit enables prolonged observations of the Earth’s bow shock and simultaneous observations of magnetic reconnection near the subsolar point and near the cusp, as well as on the flanks of the magnetosphere at both high and low latitudes. On the nightside, the combined spacecraft allow Earth’s dynamic magnetotail to be investigated, simultaneously in key regions where magnetospheric substorm onset and particle acceleration are thought to 1 School of Earth and Space Sciences, Peking University, Beijing, China. 2 Center for Atmospheric Research, University of MassachusettsLowell, Lowell, Massachusetts, USA. 3 Solar System Missions Division, European Space Research and Technology Centre, European Space Agency, Noordwijk, Netherlands. 4 Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing, China.

Copyright 2008 by the American Geophysical Union. 0148-0227/08/2008JA013146$09.00

occur. The TC-2 orbit design focused on physical processes taking place over the high-latitude magnetospheric region, the development of auroral substorms, and the intensification of the ring current. [3] Both Double Star satellites are cylindrical in shape with a diameter of 2.1 m, a height of 1.2 m, and a mass of 340 kg (Figure 2). The two Double Star spacecraft structures are identical and only differ in the communication booms. TC-1 carries one communication boom and TC-2 has two booms. In addition, two deployable 3.5 m booms are attached at the bottom of the spacecraft and carry the fluxgate and search coil magnetometers. The spin axis is set to lie perpendicular to the ecliptic and the spacecraft makes 15 rotations per minute (the same as Cluster) enabling the full, three-dimensional particle distribution functions to be measured every 4 s. [4] Each Double Star spacecraft carries eight scientific instruments to measure the magnetic field, waves, electron, ions of low and high energy, and energetic neutral atoms. The highlight aspect of Europe’s participation in Double Star program was to provide seven identical instruments (spares or duplicates) to those flying on the Cluster spacecraft.

2. Coordinated Studies of Magnetospheric Dynamic Processes [5] The launch of the two Chinese – ESA Double Star spacecraft provided a unique opportunity for coordinated multipoint measurements with the Cluster mission. The Double Star mission was designed to perform synergistic observations with Cluster in many regions of the magnetosphere. All six spacecraft orbits have apogees aligned near the same MLT. As we can see from Figure 3, from January to March the apogees of Double Star TC-1 and Cluster are in the solar wind and the apogee of Double Star TC-2 is in the polar cusp. Many conjunctions between the Cluster and Double Star have been found at the bow shock, the magnetopause, and the polar cusp. Initial results are quite impressive on comparative Cluster-Double Star measurements of the dayside magnetosphere, in particular on processes operating simultaneously at low latitudes, high latitudes, and in the cusp. From July to October, TC-1 spends most of its time in the current disruption (CD) region of the near-Earth magnetotail (8 – 10 RE), while Cluster crosses through the plasma sheet further down the tail near-Earth neutral line (NENL) formation at
19 RE

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Figure 1. Illustration of Double Star mission. The first spacecraft of the Double Star program called in Chinese ‘‘Tan Ce – 1’’ (TC-1 – Explorer-1) with an elliptical orbit of 550 km by 66,970 km, inclined at 28.5 degrees to the equator (period 27.4 h). The second spacecraft is called TC-2 (the polar satellite) having an orbit of 700 km by 39,000 km with a period of 11.7 h. (Figure 3). In the meantime TC-2 is crossing the nightside auroral zone and rapidly samples field lines that map along the length of the magnetotail. Such a constellation offers the possibility to perform convincing simultaneous timing measurements of substorm signatures in both the near-Earth tail and the near-Earth neutral line region. Together with ground-based data, the long-standing question of whether substorm activity originates in the CD region or the NENL region is being investigated. [6] This special issue provides a forum to present the results of multipoint observations from the Cluster-Double Star constellations. The main topics will be focused on investigations of the dayside and nightside, in particular on comparative magnetopause and magnetotail studies based on conjunctive data from Cluster and Double Star six spacecraft. The highlights of this special issue provide an overview of the coordinated multipoint measurements of magnetotail, magnetopause/polar cusp and inner magnetosphere. 2.1. Magnetic Reconnection, Substorm, and Storm Processes in the Magnetotail [7] Simultaneous multipoint measurements of Double Star-Cluster in the magnetotail have revealed a number of

new features of reconnection, substorm, and storm processes. The simultaneous observation of a recurrent reconnection event at unusually near-Earth location (10 –12 RE) on 26 September 2005 [Sergeev et al., 2008] demonstrates that intense reconnection can operate in short pulses in the embedded current sheets. The mapping with adapted magnetospheric model confirms that reconnection is mapped onto the localized auroral brightening region. The acceleration of electrons in the outflow region is found to be consistent with Fermi/betatron acceleration of inflow electrons after they passed through the potential drop of
180 V. The reconnection-related quadrupole magnetic field is shown to extend by at least a few tens of ion inertial lengths from the reconnection site. The concurrent strong turbulence seems not to destroy the frozen-in ion behavior in the reconnection outflow. Nakamura et al. [2008] reported a Cluster observation of an ion-scale thin current sheet in the magnetotail under the presence of a guide field. Large fluctuations in BY (not seen in IMF) suggest that a varying reconnection rate causes a varying transport of BY-dominated magnetic flux. The strong current with a peak current density of 182 nA/m2 is found to be mainly a field-aligned

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Figure 2. Photo of Double Star (TC-1) spacecraft. Double Star satellites are cylindrical in shape with a diameter of 2.1 m, a height of 1.2 m, and a mass of 340 kg. The allocations of visible instruments in the TC-1 picture are indicated. current flowing close to the center of the plasma sheet, implying that electrons moving mainly along the field lines can contribute to a strong dawn-to-dusk current when the magnetotail current sheet is sufficiently thin and active in a strong guide field case. A short duration burst of electrons above 2– 3 keV and up to 100 keV, streaming away from a reconnection region, was observed when four Cluster satellites were crossing the near Earth plasma sheet on 18 August 2002 [Aasnes et al., 2008]. These electrons were aligned with the magnetic field on both the northern and southern side of the current sheet, indicating the acceleration process to be highly localized and/or bursty. [8] Furthermore, comparisons of Cluster and TC2 measurements provide further evidence for asymmetry of physical processes in the earthward/tailward reconnection outflow regions [Voros et al., 2008]. The multiscale magnetic fluctuations in the tailward region are characteristic for MHD cascading turbulence in the presence of a local mean magnetic field, while fluctuations in the earthward region are exhibiting more power, lack of variance, and scaledependent anisotropies. Of great interest are also further observations of the anticorrelation between the Hall ( j  B) and r . Pe terms in Ohm’s law in the plasma sheet [Henderson et al., 2008]. The results confirm that the anticorrelation between these two terms is general and linear and that the contributions to the electric field are mainly in the direction normal to the neutral sheet, whereas the directional organization observed by Henderson et al. [2006] appears when a large cross-tail current is present.

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[9] Study of multiscale substorm processes is one of key scientific objectives of Double Star-Cluster coordinated measurements. X. Cao et al. [2008] present two case studies of substorm timing with TC1, Cluster, Polar, IMAGE, LANL satellites, and ground-based measurements. They show that 8 – 10 min ahead of the auroral breakup, Cluster measured an earthward flow associated with plasma sheet thinning. A couple of minutes after the breakup, TC1 detects plasma sheet expansion and subsequently the geostationary satellites measure energetic electron injections. About 20 min later, Cluster and Polar successively observe plasma sheet expansion. Substorm dipolarization seems to begin around X
(8 – 9) RE, then progresses both earthward and tailward. They also found that auroral bulge is quickly expanding poleward when the open magnetic flux in the polar cap is rapidly dissipated during tail lobe reconnection., Lui et al. [2008] investigated a substorm on 3 October 2004 during which 11 satellites were located in near-Earth magnetotail (XGSM > 10 RE). The temporal sequence of substorm activity revealed by these satellites indicates that the substorm expansion was initiated close to the Earth and spread later to further downstream distances. TC-1 and Cluster data show that there is no close relationship between some dipolarizations and earthward plasma flows in the near-Earth region. Analysis of the dawn-dusk magnetic perturbations suggests that these could be caused by a substorm current system consisting of not only the azimuthal closure of field-aligned current (the substorm current wedge) but also the meridional closure of field-aligned current. A fortuitous conjunction event on 26 September 2004 observed by Cluster, Double Star TC1, and MIRACLE magnetometer stations at almost the same local time has been investigated by Takata et al. [2008]. The different polarity of BY, Cluster curlometer current density, and the curl of the equivalent current on the ground, show that the associated current system resembles that of a bubble model [Pontius and Wolf, 1990], i.e., the propagation of a fast-moving flux tube with field-aligned currents (FACs) on each side of the bursty bulk flow (BBF). Another Cluster, TC1, and IMAGE conjunction event was reported by Volwerk et al. [2008]. The magnetic phenomena at the earthward site of a magnetic reconfiguration region are shown to be governed by field-aligned currents (FACs), which in their turn generate auroral brightenings. It is also shown that the inward and outward motion of the dipolarization front near Cluster has a direct influence on the parallel plasma flow at TC1, indicating a piston mechanism. Similar to Nakamura et al. [2008], Shen et al. [2008] also showed that the current in the thin current sheet with strong BY is field-aligned and mainly duskward and that the main current carrier is electrons. In addition, they found that the northward turning of the IMF triggers the explosive growth phase at the end of the growth phase. During the explosive growth phase which lasts for several minutes, the flattened current sheet becomes much thinner and the current density increases considerably. Just after the onset of the substorm, the current density drops abruptly and varies turbulently. Runov et al. [2008] reported that on 28 August 2005 a substorm started in a localized region near midnight. A thin current sheet with a thickness of less than 900 km and current density of
30 nA/m2 was observed during about 6 min around the substorm onset. A tailward flow with a

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Figure 3. A schematic illustration of Double Star TC-1 and 2 and Cluster constellations during (top) spring and (bottom) fall seasons. The location of the bow shock, magnetosheath, the magnetopause, the inner magnetosphere trapping region, the tail lobe, and the neutral sheet region are indicated. peak of 800 km/s occurred prior to the onset, and then reversed to earthward coinciding with a Bz turning. These observations help to reveal the activities in the tail current sheet around substorm onset. J.B. Cao et al. [2008] shows that the bursty bulk flows (BBFs) in the near-Earth plasma sheet excite simultaneously long-period Pi2 (90 – 130 s) and short-period Pi2 (
50 s). The former is associated with the field-aligned current (FAC) produced by the braking of BBFs. The time difference between the onset time of the BBFs at Cluster and the starting time of the Pi2 on the ground is very close to the propagation time of Alfven waves from Cluster position to the Earth. The latter is shown not to be excited by nightside current system but likely a global cavity mode. [10] Another highlight is the observation of O+ behaviors during storm times. Echer et al. [2008] observed a fieldaligned O+ outflow in the plasma sheet boundary layer during the initial phase of the 17 August 2001 magnetic

storm when the interplanetary shock caused a large compression of the magnetosphere. The escape rate of O+ into the magnetotail was found to be 4.0  1024/s, which is about 20 times the O+ inflow into the ring current during an intense magnetic storm. The availability of coordinated measurement data from spacecraft Double Star/Cluster constellations offers the unique possibility to perform simultaneous timing measurements of plasmoids, flux ropes, and flux transfer events signatures in the magnetosphere. Zong et al. [2008] reported two extremely O+-rich BBF events observed simultaneously by Cluster and TC1 on 8 November 2004 during a strong storm time period with Dst = 373 nT. The O+ densities and thermal pressures are 3– 5 times and 8 times larger than the H+ ones, respectively, so that the flow braking region should be greatly pushed inside the usual pressure balance region into the inner magnetosphere. The signatures of two BBFs are observed by GOES 10 at the geosynchronous altitude near midnight.

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These observations demonstrate that O+ dominated BBFs can be formed during strong storm times and that O+ embedded in the BBFs could be carried by BBFs into the ring current region. [11] Finally, Pedersen et al. [2008] pointed out that spacecraft potential measurements by the EFW electric field experiment on the Cluster satellites can be used to obtain plasma density estimates in the lobes and plasma sheet, which is of particular importance for studies of reconnection and substorm and storm processes when other experiments on Cluster have intrinsic limitations. Typical examples have been presented to demonstrate the use of this technique in the lobe plasma. Besides, there have been many studies on occurrence of plasma bubble in the past. Observations with in situ measurements were largely affected by the satellite orbit and altitude. Nishioka et al. [2008] reported the first study of bubble occurrence based on GPS data from 2000 to 2006 from 23 GPS receivers around the dip equator. This might lead to an unprecedented view of occurrence characteristic of plasma bubble and help to better understand the process of plasma bubble generation. 2.2. Fine Structures Observed at the Bow Shock, the Magnetopause, and the Cusp [12] Using Cluster spacecraft the physical properties of the bow shock can be for the first time fully quantified. Lucek et al. [2008] have shown that the shock thickness can be smaller than 2500 km for time periods around 10 min and even smaller than 1000 km during shorter time durations. Downstream of the shock, near the magnetopause, the Cluster-Double Star orbits have proven essential to investigate the properties of the magnetopause at low and high latitudes quasi-simultaneously. The wave power observed by Double Star near the equatorial plane was systematically stronger than the power observed at high latitude by Cluster [Cornilleau-Wehrlin et al., 2008]. [13] Owen et al. [2008] used a line configuration of Cluster to study a ‘‘crater’’ flux transfer event (FTE). The FTE was moving at a fraction of the magnetosheath flow and producing a traveling magnetopause erosion region in its wake. Daum et al. [2008] modeled an FTE event observed by ground-based SuperDARN radars and Cluster using MHD simulation combined with a model of flux tube motion (cooling). They could estimate the spatial and temporal evolution of the FTE. Pitout et al. [2008] investigated properties of the magnetosheath and the magnetopause during a crossing of TC-1 and Cluster at low and high latitudes, respectively. First, one FTE was found at low latitude and not at high latitude, then a bulge was observed to progress along the magnetopause, and finally after a northward turning of the magnetic field in the magnetosheath, a reverse FTE was observed at high latitude. [14] Debate in the process of reconnection has been ongoing since a few years between antiparallel and component reconnection geometry. Multipoint Cluster-Double Star results show that they both occur at the same time at different places when the IMF has a nonnull azimuthal component [Berchem et al., 2008; Dunlop et al., 2008; Pu et al., 2007]. Although reconnection with Hall effects has been reported many times in the tail, Zhang et al. [2008] made the first observations of Hall reconnection near the cusp region. Trenchi et al. [2008] studied reconnection jets at the

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magnetopause under various magnetosheath parameters: local Alfven Mach number, plasma beta, and magnetic shear angle. The observations indicate the presence of a reconnection line hinged near the subsolar point and tilted according to the observed magnetosheath clock angle, consistent with the component merging model. [15] Mapping between the low-latitude boundary layer, at the equatorial magnetopause, and the midaltitude cusp was made and revealed similar reclosed and open regions under northward IMF-Bz [Bogdanova et al., 2008]. Finally, the quick reaction of the cusp after the turning northward of the IMF was investigated [Escoubet et al., 2008; Hu et al., 2008] and temporal ion injections observed in the midaltitude cusp were shown to be produced by the change of the reconnection rate at the magnetopause [Trattner et al., 2008]. 2.3. Dynamic Process in the Inner Magnetosphere [16] Three-dimensional density and wave structures on large, medium, and small scales in the outer regions of the plasmasphere can also be unraveled by using dedicated multipoint analysis tools based on the Cluster and Double Star data set. During geomagnetic active time wave-particle interaction can account for local acceleration, radial transport across L shells, and the loss of radiation belt population. Simultaneous wave and particle measurements from Cluster and Double Star satellites during conjunctions are key to understand and quantify the effects of wave-particle interaction on the trapped energetic electron populations in the outer radiation belt. [Zong et al., 2007]. [17] Coordinated plasma ion measurements obtained by the CIS and HIA instruments onboard Cluster and Double Star TC-1 provide a systematic survey on the ring current and the plasmasphere ion environment. Multiple nose-like structures are often observed simultaneously by both Cluster and TC-1 spacecraft. The Cluster-Double Star constellation provides a unique opportunity to nose-like event in expended spatial and temporal aspects. The CIS/Cluster and HIA/Double Star instrument provide wider energy band (5 eV to 40 KeV) and ion composition information for the ion dynamic in the inner magnetosphere. These observations should pose a challenge for the simulation and modeling of the inner magnetosphere plasma and energetic particle dynamic evolution during different geomagnetic conditions [Dandouras et al., 2008]. The energetic neutral atom images measured by the Neutral Atom Detector Unit (NUADU) on board Double Star TC-2 during a geomagnetic storm on 8 May 2005 is presented by Tang and Lu [2008]. The ring current ion fluxes deduced from the NUADU measurements are in agreement with the results from the Comprehensive Ring Current Model (CRCM). This consistency indicates that ENA measurements can provide a global ring current ion distribution and dynamics during magnetic storms. The field aligned current filaments with outflow electrons from the ionosphere have been observed by both FAST and Cluster spacecraft. Upgoing electrons with energy of a few hundred eV, suggesting substantial electron acceleration occurred below FAST’s altitude of 3200 km [Wright et al., 2008]. The current filaments have a perpendicular scale of a few hundred kilometers as observed by Cluster tetrahedral (which maps to a few tens of kilometers at FAST). The inner magneto-

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sphere and the plasma sheet response to passage of an interplanetary shock on 24 August 2005 have been discussed by using joint Cluster and Double Star constellation [Keika et al., 2008]. It is found that interplanetary shock produced magnetic and electric field disturbances propagating from both the dayside and flank magnetopauses to the tail plasma sheet. In addition, no substorm activity was observed during the passage of the shock [Keika et al., 2008].

3. Summary [18] This special issue provides an opportunity to document the latest results of multipoint observations from the Cluster-Double Star constellations as well as from other spacecraft. The main topics addressed are investigations of the dayside and nightside, in particular on comparative bow shock, magnetopause, cusp, magnetotail, and inner magnetosphere studies based on multiple spacecraft observations. [19] The collaboration between ESA, CNSA, the European institutes, and Chinese institutes was a human adventure since it was the first time that European hardware was flown on a Chinese-built spacecraft. Hundreds of highly motivated scientists and engineers from both sides made this mission possible. [20] In the early morning on 14 October 2007, the Double Star TC-1 satellite, the first scientific spacecraft built and operated by CNSA in cooperation with ESA returned to Earth after more than doubling its designed orbit lifetime. TC-2 will, however, continue to provide the near-Earth polar region measurements as well as the monitoring of Energetic Neutral Atom in the ring current. [21] Acknowledgments. We gratefully acknowledge the ESA Director of Science, David Southwood; the former ESA Director of Science, Roger Bonnet; the CNSA Administrator, Sun Lai Yan; the former CNSA Administrator, Luan Enje; the ESA Project Manager, Bodo Gramkow; the CSSAR Director, Wu Ji; the Principal Engineer of the Double Star program, Shigeng Yuan; as well as the European and Chinese Principal Investigators.

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Dunlop, M. W., M. Taylor, Y. Bogdanova, C. Shen, F. Pitout, Z. Y. Pu, J. Davies, Q. H. Zhang, and J. Wang (2008), Energisation in the electron boundary layer: Cluster/double star observations at high and low latitude, J. Geophys. Res., doi:10.1029/2007JA012788, in press. Echer, E., et al. (2008), Cluster observations of O+ escape in the magnetotail due to shock compression effects during the initial phase of the magnetic storm on August 17, 2001, J. Geophys. Res., 113, A05209, doi:10.1029/2007JA012624. Escoubet, C. P., et al. (2008), The effect of a northward turning of the imf on cusp precipitation as observed by cluster, J. Geophys. Res., 113, A07S13, doi:10.1029/2007JA012771. Henderson, P. D., C. J. Owen, A. D. Lahiff, I. V. Alexeev, A. N. Fazakerley, E. Lucek, and H. Reme (2006), Cluster peace observations of electron pressure tensor divergence in the magnetotail, Geophys. Res. Lett., 33, L22106, doi:10.1029/2006GL027868. Henderson, P. D., C. J. Owen, A. D. Lahiff, I. V. Alexeev, A. N. Fazakerley, L. Yin, A. P. Walsh, E. Lucek, and H. Reme (2008), The relationship between j  B and r  Pe in the magnetotail plasma sheet: Cluster observations, J. Geophys. Res., 113, A07S31, doi:10.1029/2007JA012697. Hu, R., et al. (2008), Cluster observations of the mid-altitude cusp under strong northward interplanetary magnetic field, J. Geophys. Res., doi:10.1029/2007JA012726, in press. Keika, K., et al. (2008), Response of the inner magnetosphere and the plasma sheet to a sudden impulse, J. Geophys. Res., 113, A07S35, doi:10.1029/2007JA012763. Liu, Z. X., C. P. Escoubet, Z. Pu, H. Laakso, J. K. Shi, C. Shen, and M. Hapgood (2005), The Double Star mission, Ann. Geophys., 23, 2707 – 2712. Lucek, E. A., T. Horbury, I. Dandouras, and H. Reme (2008), Cluster observations of the Earth’s quasi-parallel bow shock, J. Geophys. Res., 113, A07S02, doi:10.1029/2007JA012756. Lui, A. T., et al. (2008), Near-Earth substorm features from multiple satellite observations, J. Geophys. Res., 113, A07S26, doi:10.1029/2007JA012738. Nakamura, R., et al. (2008), Cluster observations of an ion-scale current sheet in the magnetotail under the presence of a guide field, J. Geophys. Res., 113, A07S16, doi:10.1029/2007JA012760. Nishioka, M., A. Saito, and T. Tsugawa (2008), Occurrence characteristics of plasma bubble derived from global ground-based GPS receiver networks, J. Geophys. Res., 113, A05301, doi:10.1029/2007JA012605. Owen, C. J., et al. (2008), Cluster observations of ‘‘crater’’ flux transfer events at the dayside high-latitude magnetopause, J. Geophys. Res., 113, A07S04, doi:10.1029/2007JA012701. Pedersen, A., et al. (2008), Electron density estimations derived from spacecraft potential measurements on Cluster in tenuous plasma regions, J. Geophys. Res., 113, A07S33, doi:10.1029/2007JA012636. Pitout, F., M. W. Dunlop, A. Blagau, Y. V. Bogdanova, C. P. Escoubet, C. Carr, I. Dandouras, and A. N. Fazakerley (2008), Coordinated Cluster and Double Star observations of the dayside magnetosheath and magnetopause at different latitudes near noon, J. Geophys. Res., doi:10.1029/ 2007JA012767, in press. Pontius, D. H., Jr., and R. A. Wolf (1990), Transient flux tubes in the terrestrial magnetosphere, Geophys. Res. Lett., 17, 49 – 52. Pu, Z. Y., et al. (2007), Global view of dayside magnetic reconnection with the dusk-dawn IMF orientation: A statistical study for Double Star and Cluster data, Geophys. Res. Lett., 34, L20101, doi:10.1029/2007GL030336. Runov, A., et al. (2008), Observations of an active thin current sheet, J. Geophys. Res., 113, A07S27, doi:10.1029/2007JA012685. Sergeev, V. A., et al. (2008), Study of near-Earth reconnection events with Cluster and Double Star, J. Geophys. Res., 113, A07S36, doi:10.1029/ 2007JA012902. Shen, C., et al. (2008), Flattened current sheet and its evolution in substorms, J. Geophys. Res., 113, A07S21, doi:10.1029/2007JA012812. Takata, T., et al. (2008), Local field-aligned currents in the magnetotail and ionosphere as observed by a Cluster, DSP and MIRACLE conjunction, J. Geophys. Res., doi:10.1029/2007JA012759, in press. Tang, L. C., and L. Lu (2008), A comparison of NUADU neutral atom image inversion with a comprehensive ring current model, J. Geophys. Res., 113, A07S32, doi:10.1029/2007JA012680. Trattner, K.-J., S. Fuselier, S. Petrinec, T. Yeoman, C. P. Escoubet, and H. Reme (2008), Reconnection site of temporal cusp structures, J. Geophys. Res., 113, A07S14, doi:10.1029/2007JA012776. Trenchi, L., M. F. Marcucci, G. Pallocchia, G. Consolini, M. B. Bavassano Cattaneo, A. M. Di Lellis, H. Reme, L. Kistler, C. M. Carr, and J. B. Cao (2008), Occurrence of reconnection jets at the dayside magnetopause: Double Star observations, J. Geophys. Res., 113, A07S10, doi:10.1029/ 2007JA012774. Volwerk, M., et al. (2008), Magnetotail depolarization and associated current systems observed by Cluster and Double Star, J. Geophys. Res., doi:10.1029/2007JA012729, in press.

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Zong, Q.-G., A. Korth, S. Fu, and H. Zhang (2008), Ionospheric oxygen ions dominant bursty bulk flows: Cluster and Double Star observations, J. Geophys. Res., doi:10.1029/2007JA012764, in press. 

C. P. Escoubet, Solar System Missions Division, European Space Research and Technology Centre, European Space Agency, Keplerlaan 1, NL-2200 AG Noordwijk, Netherlands. Z. X. Liu, Center for Space Science and Applied Research, Chinese Academy of Sciences, P.O. Box 8701, Zhongguancun, 100080 Beijing, China. X. Y. Pu and Q.-G. Zong, School of Earth and Space Sciences, Peking University, Yiheyuan Street, #5, 100871 Beijing, China.

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