M. Dunlop's research while affiliated with Beihang University (BUAA) and other places

Publications (238)

Article
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How does solar wind energy flow through the Earth’s magnetosphere, how is it converted and distributed? is the question we want to address. We need to understand how geomagnetic storms and substorms start and grow, not just as a matter of scientific curiosity, but to address a clear and pressing practical problem: space weather, which can influence...
Article
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The terrestrial magnetopause forms the boundary between the solar wind plasma with its embedded interplanetary magnetic field on one side, and the terrestrial magnetosphere, dominated by Earth's dipole field, on the other side. It is therefore a key region for the transfer of mass, momentum, and energy from the solar wind to the magnetosphere. The...
Article
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A novel algorithm for estimating both the linear and quadratic gradients of physical quantities based on multiple spacecraft observations using the least squares method is put forward. Using 10 or more spacecraft constellation measurements as input, this new algorithm can yield both the linear and quadratic gradients at the barycenter of the conste...
Article
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This research aims to determine the geometrical configurations of boundary surfaces in the space environment, based on multiple spacecraft measurements. To achieve this, the Normal Field Analysis (NFA) method is presented here. With multipoint observations, the three‐dimensional gradient of the normal of boundary layers can be obtained, and the pri...
Article
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When the supersonic solar wind encounters the Earth's magnetosphere a shock, called bow shock, is formed and the plasma is decelerated and thermalized in the magnetosheath downstream from the shock. Sometimes, however, due to discontinuities in the solar wind, bow shock ripples or ionized dust clouds carried by the solar wind, high speed jets (HSJs...
Preprint
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This paper addresses the fundamental science question: "How does solar wind energy flow through the Earth's magnetosphere, how is it converted and distributed?". We need to understand how the Sun creates the heliosphere, and how the planets interact with the solar wind and its magnetic field, not just as a matter of scientific curiosity, but to add...
Article
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In the analysis of in-situ space plasma and field data, an establishment of the coordinate system and the frame of reference, helps us greatly simplify a given problem and provides the framework that enables a clear understanding of physical processes by ordering the experimental data. For example, one of the most important tasks of space data anal...
Article
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This paper addresses the fundamental science question: "How does solar wind energy flow through the Earth's magnetosphere, how is it converted and distributed?". We need to understand how the Sun creates the heliosphere, and how the planets interact with the solar wind and its magnetic field, not just as a matter of scientific curiosity, but to add...
Article
The influence of the interplanetary magnetic field (IMF) cone angle θ (the angle between the IMF direction and the Sun-Earth line) on the invariant latitudes (ILATs) of the footprints of the field-aligned currents (FACs) in the magnetotail has been investigated. We performed a statistical study of 542 FAC cases observed by the four Cluster spacecra...
Article
For the first time, the current density distribution in the inner equatorial magnetosphere ranging from 4 to 12 RE (RE is the Earth radius, 6371km) has been obtained by using Time History of Events and Macroscale Interactions during Substorms (THEMIS) (P3, P4, and P5) three point magnetic measurements. This study mainly focuses on the storm events...
Article
Although the particle carriers of field-aligned currents (FACs) in the Earth's magnetotail play an important role in the transfer of momentum and energy between the solar wind, magnetosphere, and ionosphere, the characteristics of the FAC carriers have been poorly understood. Taking advantage of multi-instrument magnetic field and plasma data colle...
Article
A magnetic reconnection event detected by Cluster is analyzed using three methods: Single-spacecraft Inference based on Flow-reversal Sequence (SIFS), Multi-spacecraft Inference based on Timing a Structure (MITS), and the First-Order Taylor Expansion (FOTE). Using the SIFS method, we find that the reconnection structure is an X-line; while using th...
Article
In this paper, we report the evidence of compressible turbulence with slow mode waves in a bursty bulk flow of plasma sheet. This compressible turbulence is characterized by a multi-scale (1 - 60 s) anti-correlation between plasma density and magnetic field strength. Besides, the magnetic compressibility spectrum stays nearly constant at all the me...
Article
We studied energetic electron (40-250 keV) bursts (EEB) in the plasma sheet (PS) and their relation to bursty bulk flows (BBF) using the data recorded by Cluster from 2001 to 2009. The EEBs in the PS can be classified into four types. Three types of EEBs are dispersionless, including EEBs accompanied with BBFs (V > 250 km/s) but without DF, EEBs ac...
Article
Unambiguous knowledge of magnetic field structure and the electric current distribution is critical for understanding the origin, evolution and related dynamic properties of magnetic flux ropes (MFRs). In this paper, a survey of 13 MFRs in the Earth's magnetotail are conducted by Cluster multi-point analysis, so that their force-free feature, i.e.,...
Article
The penetration of Interplanetary Magnetic Field (IMF) By into the magnetosphere plays an important role in determining magnetospheric configuration and its dynamics. In this paper, using 9 years of Cluster data at the center of neutral sheet, we statistically study the relations of the penetration of IMF By in the neutral sheet (NS) with IMF Bz an...
Article
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Magnetic disturbances caused by the Earth's ring current, particularly during storm time activity, have a dominant effect on the geomagnetic field. Strong currents and large kinetic and magnetic energies can change considerably local field geometry, and depress the ground geomagnetic field. The multi-spacecraft magnetic measurements of Cluster allo...
Article
The influences of the interplanetary magnetic field (IMF) cone angle θ and clock angle ϕ on the field-aligned currents (FACs) at the plasma sheet boundary layers (PSBLs) have been investigated using Cluster Data. The FAC occurrence increases monotonically with IMF cone angle and has two peaks at -90° and +110° clock angle, respectively. The peak at...
Article
[1] Flux transfer events (FTEs) are magnetic flux ropes formed at planetary magnetopauses (MPs). Although evidence suggests that FTEs form through time-dependent magnetic reconnection, details of that process and 3D structure of the flux ropes remain largely unclear. This letter presents Double Star/TC-1 data of an FTE occurred on 7 April 2004 whic...
Article
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Modelling plasma entry in the polar cusp has been successful in reproducing ion dispersions observed in the cusp at low and mid-altitudes. The use of a realistic convection pattern, when the IMF-By is large and stable, allowed Wing et al. (2001) to predict double cusp signatures that were subsequently observed by the DMSP spacecraft. In this paper...
Article
The influence of the interplanetary magnetic field (IMF) By component on the field-aligned currents (FACs) in the plasma sheet boundary layer (PSBL) in the magnetotail during the northward IMF were investigated using the data from Cluster. There are 748 FACs cases selected to do analysis. We present that the IMF By component plays a very important...
Article
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1] In this exploration, it is revealed for the first time that the full magnetic field gradient and current density distribution can be derived from two spacecraft magnetic field measurements under the assumptions that the magnetic field is approximately stationary and force-free, conditions which are particularly relevant to low altitude regions o...
Article
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A moderately intense substorm on 1 March 2008, from 0830 to 1000 UT, observed by THEMIS probes and the Ground Based Observatory (GBO) is examined to investigate the global evolution of substorm phenomena. During this interval, all five THEMIS probes are closely aligned along the tail axis near midnight covering a radial range from ˜9 Re to ˜18 Re....
Article
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A data set of the Cluster cusp crossings over a 5-year period is studied for the interhemispheric comparison of the dipole tilt angle effect on the latitude of the mid-altitude cusp. The result shows that the dipole tilt angle has a clear control of the cusp latitudinal location. Although, the northern cusp moves 0.054° ILAT for every 1° increase i...
Article
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The aurorae are dynamic, luminous displays that grace the night skies of Earth's high latitude regions. The solar wind emanating from the Sun is their ultimate energy source, but the chain of plasma physical processes leading to auroral displays is complex. The special conditions at the interface between the solar wind-driven magnetosphere and the...
Article
This paper investigates the structure of the magnetic field near the magnetopause (MP) by analyzing the multiple-point magnetic measurements from the Cluster mission. In this paper, the spatial distribution of the curvature radius of the MP surface at the noon-midnight meridian and for situations with moderate dynamical pressure of solar wind is im...
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No abstract available.
Article
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The penetration of plasma sheet ions into the inner magnetosphere is very important to the inner magnetospheric dynamics since plasma sheet ions are one of the major particle sources of ring current during storm times. However, the direct observations of the inner boundary of the plasma sheet are fairly rare due to the limited number of satellites...
Article
The Kelvin Helmholtz Instability can drive waves at the magnetopause. These waves can grow to form rolled up vortices and facilitate transfer of plasma into the magnetosphere. We use single spacecraft measurements from the Double Star one spacecraft to identify rolled up vortices and present their local time distribution. This work is being carried...
Article
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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 2002. The occurrence rate of earthward BBFs increases with distance from the Earth up to −19 RE, which is in agreement with the previous observations of t...
Article
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This paper was published as Journal of Geophysical Research, 2010, 115, A07228. Copyright 2010 by the American Geophysical Union. It is also available from http://www.agu.org/pubs/crossref/2010/2009JA014446.shtml. Doi: 10.1029/2009JA014446 We statistically investigated features of the field-aligned current (FAC) distribution in plasma sheet boundar...
Article
A robust multiscale analysis of high‐frequency magnetic field measurements from the Cluster spacecraft is presented using complimentary measurements from the magnetometer and search‐coil instruments; in a stationary interval of fast ambient solar wind. We show a surprising and novel result: that for time‐scales smaller than the ion‐gyro period the...
Article
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We investigate the spatial variation of magnetopause energy conversion and transfer using Cluster spacecraft observations of two magnetopause crossing events as well as using a global magnetohydrodynamic (MHD) simulation GUMICS-4. These two events, (16 January 2001, and 26 January 2001) are similar in all other aspects except for the sign of the in...
Chapter
In this paper, we have considered the view that the Martian magnetic moment has been gradually decreasing from the past to the present, and have calculated the O+ ion flux distribution along magnetic field lines and the escaping ion flux in the Martian tail with different assumed Martian magnetic moments. The results show that the O+ ions flux alon...
Article
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Strong interplanetary shock interactions with the Earths magnetosphere have great impacts on energetic particle dynamics in the magnetosphere. An interplanetary shock on 7 November 2004 (with the maximum solar wind dynamic pressure of ∼70 nPa) was observed by the Cluster constellation to induce significant ULF waves in the plasmasphere boundary, an...
Article
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Two vortex-like plasma flow structures have been observed at the outer radiation belt and/or the ring current region on 11 April 2002, from 0415 to 0635 UT, when the Cluster fleet entered (in the Southern Hemisphere) and exited (in the Northern Hemisphere) the boundary layer of the inner magnetosphere near 2130 MLT. On 11 April 2002 during the peri...
Article
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In this article, we study the velocity distribution, density, duration, and energy transport of earthward flow bursts in the inner plasma sheet (IPS) during three substorm phases using the data of Cluster in 2001 and 2002. The mean peak velocity of earthward flow bursts in recovery phases (390 km/s) is smaller than those in growth and expansion pha...
Article
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By analyzing hot ion and electron parameters together with magnetic field measurements from Cluster, an event of magnetopause crossing of the spacecraft has been investigated. At the latitude of about 40° and magnetic local time (MLT) of 13:20 during the southward interplanetary magnetic field (IMF), a transition layer was observed, with the magnet...
Article
In this research, the properties of a tail current sheet, which has a flattened geometry, and its evolution during substorm activity have been investigated. The geometrical configuration of the magnetic field and the spatial distribution of the current density in a flattened current sheet have been revealed with certainty for the first time. It is...
Article
Based on multiple spacecraft measurements, the geometrical structures of tilted current sheet and tail flapping waves have been analyzed and some features of the tilted current sheets have been made clear for the first time. The geometrical features of the tilted current sheet revealed in this investigation are as follows: (1) The magnetic field li...
Article
ULF magnetic turbulence in the external terrestrial cusp and adjacent regions at southward IMF conditions is studied on the base of the Cluster measurements with applying the advanced phase difference method for the data analysis. The contribution of the coherent oscillations in the turbulence energy has been estimated, and wave energy distribution...
Article
Field aligned current (FAC) distribution in the plasma sheet boundary layers (PSBLs) in the magnetotail is studied statistically by analysing magnetic field data from the Cluster 4-point measurements. The results show that the FAC distribution on the dusk side is not the same as that on the dawn side in the magnetotail. On the each side earthward a...
Article
We present the results of three-dimensional magnetohydrodynamic (MHD) and large-scale particle (LSK) simulations of the response of the cusp to an abrupt rotation of the interplanetary magnetic field (IMF). The study is based on Cluster measurements on 23 September 2004. During the event the four satellites crossed the polar cusp within 2-16 minute...
Article
The polar cusps are two regions of the magnetosphere where the influence of the interplanetary magnetic field (IMF) is particularly strong. When the IMF is southward the plasma enters the cusp around the subsolar point or near the equatorward boundary of the cusp and on the other hand when the IMF is northward, the plasma enters through the lobes o...
Article
The CLUSTER mission has provided a considerable number of in-situ observations of the formation of an X- line in the mid-tail region of the Earth's magnetotail shedding light on the physical processes underlying time- dependent collisionless reconnection during quiet as well as storm conditions. From these observations it has become evident that th...
Article
Full-text available
In this research, the geometrical structures of tilted current sheet and tail flapping waves have been analysed based on multiple spacecraft measurements and some features of the tilted current sheets have been made clear for the first time. The geometrical features of the tilted current sheet revealed in this investigation are as follows: (1) The...
Article
Full-text available
In this research, the geometrical structures of tilted current sheet and tail flapping waves have been analysed based on multiple spacecraft measurements and some features of the tilted current sheets have been made clear for the first time. The geometrical features of the tilted current sheet revealed in this investigation are as follows: (1) The...
Article
Full-text available
The interaction of a tangential discontinuity (TD) and accompanying dynamic pressure increase with the Earth's bow shock launches a fast shock that travels ahead of the TD in the magnetosheath and carries a significant portion of the pressure change. In this event study, we use observations from the Cluster spacecraft and magnetohydrodynamic simula...
Article
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In this paper, we introduce an effective processing method to acquire the time derivative 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 o...
Article
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The equatorial and polar satellites of the Double Star Project (DSP) were launched successfully on December 29, 2003 and July 25, 2004, respectively, and both of them are operating smoothly. The DSP provides a good opportunity for investigating the structure of the magnetosphere. Based on the DSP data collected during 2004, we have surveyed the dis...
Article
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An event of Cluster-Double Star conjunction observations of magnetic reconnection at high latitude magnetopause nightside of both cusps and solar wind transport into magnetosphere caused by such reconnection process has been investigated. During northward IMF, Cluster/SC1 observed accelerated flows and ion heating associated with magnetic reconnect...
Article
Full-text available
In this research, the properties of a tail current sheet, which has a flattened geometry, and its evolution during substorm activity have been investigated. The geometrical configuration of the magnetic field and the spatial distribution of the current density in a flattened current sheet have been revealed with certainty for the first time. It is...
Article
Full-text available
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...
Article
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A physical model for the existence of bipolar structures in the electric field that are parallel to the magnetic field and observed in the auroral ionosphere, is established by deriving the "Sagdeev potential" from the two-fluid equations in a cylindrical coordinate system. The model shows that the bipolar electric field structure can develop not o...
Article
Using a period of internal burst mode data from the Cluster Electric Field and Wave instrument a number of electrostatic solitary structures have been identified in the foot region of Earth's quasi-perpendicular bow shock. The four individual probe potential measurements are utilized to investigate the fundamental characteristics of the solitary wa...
Article
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This study uses two conjunctions between Cluster and Double Star TC-1 spacecraft together with global magnetohydrodynamic (MHD) simulations to investigate the large-scale configuration of magnetic reconnection at the dayside magnetopause. Both events involve southward interplanetary magnetic fields with significant By components. The first event oc...
Article
Using multipoint measurements from the Cluster mission wave identification techniques are applied to observations of ULF waves made in the terrestrial foreshock with the aim of identifying the modes and properties of the waves taking into account the effects of a high beta plasma. The wave properties in the spacecraft and plasma rest frames are exp...
Article
Measurements from multi-spacecraft mission offer a unique opportunity to investigate the large-scale topology and dynamics of magnetic reconnection at the dayside magnetosphere. Recent comparisons of 3D global magnetohydrodynamic (MHD) simulations with observations for the April 6, 2004 conjunction event between the Double Star (TC1) and Cluster sp...
Article
The scale of the collisionless shock is important to study the shocks because it is directly connected with the nature of the shock and with its formation due to the balance between the steepening of a nonlinear waves in the plasma and some counteracting process. The shock scale is also one of the key parameters to determine the acceleration of the...
Article
Nonlinear, small scale electric field structures are recognized as an ubiquitous phenomenon in space plasma. However, their role in the processes of energy, momentum, and charge redistribution is still unclear. Using Cluster EFW data we analyze a number of instances of uni/bi/tri-polar electrostatic solitary waves observed in the weakly magnetized...
Article
On March 13, 2007, there was a sequence of auroral and contemporaneous magnetotail activity that occurred during a period when the THEMIS constellation was in the evening sector inner CPS. The satellites were magnetically conjugate to the auroral zone in western Canada. The viewing conditions over numerous All-Sky Imagers (ASIs) in Canada were exce...
Article
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We investigate the magnetic structure of a small earthward-moving flux rope observed by Cluster in the near-Earth plasma sheet through application of the Grad-Shafranov (GS) technique to reconstruct the transverse magnetic field distribution perpendicular to the flux rope axis at X=-14.75 R<sub>E</sub> . We find that the principal axis of the flux...
Article
ULF waves in the terrestrial foreshock observed simultaneously by the four Cluster satellites were analyzed to identify the plasma wave modes and to study the effect of plasma beta on the intrinsic wave properties. The wave properties in the spacecraft and solar wind frames, such as the wave frequency, total wave number, phase speed, and wave polar...
Article
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An analysis technique, termed MRA (magnetic rotation analysis), has been designed to probe three-dimensional magnetic field topology. It is based on estimating the gradient tensor of four-point measurements of the magnetic field which have been taken by the Cluster mission. The method first constructs the symmetrical magnetic rotation tensor and in...
Article
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1] Observations of whistler emissions are common in the magnetosphere near the dayside magnetopause. We show that one of the major source regions for these emissions is magnetic field minima that form along magnetic flux tubes at high latitudes. Using multispacecraft Cluster observations we experimentally confirm for the first time the existence of...
Article
The bipolar electric field structures were observed in many space plasmas, such as the solar wind, magnetosheath, magnetotail, and the auroral zone. In this study, a physical model for the existence of the bipolar electric field structures propagating along the magnetic field line is established by deriving the "Sagdeev potential" from the magnetoh...
Article
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High-magnitude magnetic barriers in space and solar plasma are proposed to be attributed to the pile up of magnetic field lines and their Alfvénic collapse for MHD flows. The analysis of experimental data from both the Interball and Cluster spacecrafts shows that high-magnitude magnetic structures found in the Earth magnetosheath and near the magne...