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| 1 | Differences between onset times of bursty bulk flows (BBFs) of two Cluster satellites in the magnetotail显示文摘This paper using the dataset of BBFs (bursty bulk flows) observed by two Cluster satellites C1 and C4 studies the difference between onset times of BBFs observed by C1 and C4. It is found that the onset time differences of most of BBFs observed by C1 and C4 are smaller than 60 s. The average onset time difference of BBFs of C1 and C4 is 68.5 s. The probabilities of onset time difference of BBFs of C1 and C4 larger than 30 60 90 and 120 s are respectively 55% 35% 27% and 23%. The largest onset time difference of BBFs of C1 and C4 decreases with the increase of earthward component of maximum velocities of BBFs. The onset time difference of BBFs of C1 and C4 results from the velocity inhomogeneity inside the flow channel of BBF which may be produced in propagation path and/or in source region of BBFs. Such a wide range of onset time difference of BBFs suggests that the velocity inhomogeneity inside the flow channel of BBF is various. These results are very important to the current study of substorm research based on THEMIS data because they indicate that it is impossible to determine the onset time of BBF with a single satellite. | CAO JinBin WANG ZhiQiang MA YuDuan CAI CunLin | 2012 | Science China(Technological Sciences)2012，55，5： | 8 |
| 2 | Multi-spacecraft observations of earthward flow bursts显示文摘On the basis of the plasma, electric and magnetic fields jointly observed by Cluster and the Double Star TC-1 spacecraft in the Earth's magnetotail, we have investigated the earthward flow bursts by introducing the momentum equation in the X-direction in the ideal conditions of magneto hydrodynamics (MHD). One earthward flow burst with a peak in excess of 500 km/s was selected, when the four spacecraft of Cluster were located around ?16 RE and TC-1 was located around ?10 RE in the X-direction. The inter-spacecraft distances in Y and Z directions were smaller than the statistical spatial scales of the bursty bulk flows. When the Y components of E and ?V×B were compared, there was no clear breakdown of the frozen-in condition during the earthward flow burst. With the measured plasma and magnetic parameters from two spacecraft at different positions in the magnetotail, the X component of the pressure gradient was calculated. Magnetic tension was calculated using the magnetic field measured at four points, which could be compared with the assumed constant in the past research with single satellite. When the pressure gradient and the magnetic tension were put into the MHD momentum equation, some samples of the earthward flow bursts were accelerated and some were decelerated. The braking process of the earthward flow burst was more complicated than what the past results had shown. The accelerated samples accounted for about one third of the whole earthward flow bursts and discontinuously located among the decelerated elements. The original single earthward flow burst event might be split into several short flow bursts when it was moving to the Earth. Our results may partly illustrate that the duration of fast flows during three phases of substorm becomes short near the Earth. The results are consistent with the past results that fast flows intrude to places earthward the typical braking region. | MA YuDuan CAO JinBin REME Henry DANDOURAS Iannis DUNLOP Malcolm LUCEK Elisabeth | 2012 | Science China(Technological Sciences)2012，55，5： | 8 |
| 3 | MHD and kinetic analysis of flow bursts in the Earth's plasma sheet显示文摘In an attempt to study the flow bursts in the Earth’s plasma sheet we select an event that took place on August 7,2004 in the expansion phase of a substorm,using data from the geomagnetic index,solar wind data,plasma and magnetic field observations from C1 Cluster satellite(the Cluster mission has 4 satellites)and from Double Star TC-1 satellite.In MHD approach,TC-1 firstly observed the tailward flow,then the earthward,and finally the flow alternated in two directions.C1 firstly observed the earthward plasma flow,and then the tailward plasma flow.Before flow bursts are observed by TC-1 and C1,there are disturbances in local entropy with their tailward local entropy larger than those of the earthward.The kinetic features of the plasma flow observed by C1 are similar to those in MHD.However,kinetic characteristics of the plasma flow observed by TC-1 are far more than the description in MHD.The inadequacy mainly exists in two cases:(i)the firstly enhanced tailward flows given in MHD are found without significant increase of the energetic tailward flux;(ii)the almost stagnant flow in MHD is composed of the enhanced energetic ion flux in both earthward and tailward directions.The earthward flow burst observed by TC-1 might be multiple overshoots and rebounds.The earthward flow burst observed by C1 might be simply rebounded in the near-Earth.The pulsation observed by C1 is earlier than that observed by TC-1 with the former intensity less than that of the latter.After the energetic ion flux in the tailward direction is significantly enhanced,the power spectrum intensity of the ULF wave commences to increase obviously,which may suggest that the stream instability is closely correlated with ULF pulsations. | MA YuDuan CAO JinBin FU HuiShan REME H. DANDOURAS I. YANG JunYing WANG ZhiQiang TAO Dan YANG Jian | 2014 | Science China(Technological Sciences)2014，57，1： | 7 |
| 4 | Cluster observations of large-scale southward movement and dawnward-duskward flapping of Earth's magnetotail current sheet显示文摘In August 2001,Cluster satellites observed that the mid-tail current sheet(CS) moved southward continuously for almost seven hours.Meanwhile,Cluster crossed back and forth the CS repeatedly.This means that the large-scale southward movement of the CS was accompanied by a small-scale CS flapping during this period.Using the minimum-variation-analysis(MVA) method and the multi-spacecraft data,we calculated the normal vector,current density and the magnetic curvature of the CS,the results showed that the CS alternated between flattened CS and tilted CS for several times.Strong dawn-dusk oscillations were found for the tilted CS,which caused the repeated crossings of the center of CS by the satellites.This feature is obviously different from the previous observations of the vertical flapping of the CS induced by the kink instability.Two types of flapping were observed:One of them is accompanied with bursty bulk flows(BBFs) and the other is not.This suggests that in this event there was no direct relationship between the CS flapping and BBFs. | DUAN AiYing CAO JinBin MA YuDuan WEI XinHua | 2013 | Science China(Technological Sciences)2013，56，1： | 6 |
| 5 | The mid-high latitude whistler mode chorus waves observed around substorm onsets显示文摘Using the data of LFEW/TC-2, we studied the dawn side chorus around substorm onsets during a strong geomagnetic storm in November 2004. During this storm, LFEW/TC-2 observed 14 dawnside chorus events. Nine of them were associated with substorms and occurred within 40 min around the substorm onsets. The fre-quencies of waves have a very good correlation with the half equatorial electron cyclotron frequencies. Chorus can be excited in the region near magnetic equato-rial plane and then propagate to the mid and high latitudes. When the wave fre-quencies reach the local lower hybrid frequencies, chorus can be reflected due to the lower hybrid resonance. The time delay between the chorus and its echo is about 28 min. Previous observations show that the chorus can propagate at most to the magnetic latitudes of 40°. LFEW/ TC-2 found for the first time that the chorus in space could propagate to the magnetic latitude of 70°. Since most of the previous chorus observations are made close to the magnetic equatorial plane, our results are important for the studies of excitation and propagation of whistler mode wave, and relevant relativistic electron acceleration in the magnetosphere. | YANG JunYing CAO JinBin YAN ChunXiao LI LiuYuan MA YuDuan | 2008 | Science China(Technological Sciences)2008，51，10： | 6 |
| 6 | Plasma perturbations in the coexisting environment of VLF transmitter emission, lightning strokes and seismic activity显示文摘We analyzed plasma perturbations occurring in the coexisting environment of powerful VLF transmitter emission, intense lightning strokes and strong seismic activity during pregnant period. The results suggest that anomalous electron bursts with energy dispersion in the range of ~100–350 keV, forming the 'wisp' signature, are due to cyclotron resonance of electrons with monochromatic waves from the powerful NWC VLF transmitters during nighttime. The intense broad band VLF emissions (up-going 0+ whistlers) are observed while the DEMETER satellite goes through the region of intense thunderstorm activities at mid-latitudes. However, the effects of intense lightning activity and pregnant earthquake have little impact on this kind of stable energy-dispersed electron structures, despite the fact that they are presumably two primary reasons for the particle precipitation in the ionosphere. The case studied here provides us a valuable opportunity to address the various sources triggering the anomalous plasma perturbations in the ionosphere. | TAO Dan LIU WenLong MA YuDuan | 2018 | Science China(Technological Sciences)2018，61，5： | 4 |
| 7 | Case study of small scale polytropic index in the central plasma sheet显示文摘This paper studies the effective polytropic index in the central plasma sheet(CPS) by using the method of Kartalev et al.(2006), which adopts the denoising technique of Haar wavelet to identify the homogeneous MHD Bernoulli integral(MBI) and has been frequently used to study the polytropic relation in the solar wind. We chose the quiet CPS crossing by Cluster C1 during the interval 08:51:00–09:19:00 UT on 03 August 2001. In the central plasma sheet, thermal pressure energy per unit mass is the most important part in MBI, and kinetic energy of fluid motion and electromagnetic energy per unit mass are less important. In the MBI, there are many peaks, which correspond to isothermal or near isothermal processes. The interval lengths of homogenous MBI regions are generally less than 1 min. The polytropic indexes are calculated by linearly fitting the data of lnp and lnn within a 16 s window, which is shifted forward by 8 s step length. Those polytropic indexes with |R|≥0.8(R is the correlation coefficient between lnp and lnn) and p-value≤0.1 in the homogeneous regions are almost all in the range of [0, 1]. The mean and median effective polytropic indexes with high R and low p-value in homogeneous regions are 0.34 and 0.32 respectively, which are much different from the polytropic index obtained by traditional method(?trad=?0.15). This result indicates that the CPS is not uniform even during quiet time and the blanket applications of polytropic law to plasma sheet may return misleading value of polytropic index. The polytropic indexes in homogeneous regions with a high correlation coefficient basically have good regression significance and are thus credible. These results are very important to understand the energy transport in magnetotail in the MHD frame. | PANG XueXia CAO JinBin LIU WenLong MA YuDuan LU HaoYu YANG JunYing LI LiuYuan LIU Xu WANG Jing WANG TieYan YU Jiang | 2015 | Science China Earth Sciences2015，58，11： | 2 |
| 8 | Comparison of BBFs Observed by Single and Multi Satellites显示文摘This paper,using the data of three Cluster satellites,compares the observations of Bursty Bulk Flow (BBF) by single satellite with those by multi satellites.The results indicate that there exists remarkable difference between observations of BBF by single satellite and multi satellites.The observations of BBF by a single satellite depend on its position relative to the flow channel.The difference is caused by the localization characteristics of fast flows in the plasma sheet,and can lead to diverging views about substorm and causal relations among substorm phenomena. | Cao Jinbin Cheng Chao Ma Yuduan Cai Chunlin | 2010 | 空间科学学报2010，30，4： | 1 |
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