Characteristics of ULF waves associated with the solar wind deceleration in the Earth＇s foreshock on 6-7 April 2003 is studied using the wave telescope technique. In the satellite frame, the ULF waves are the left-ha...Characteristics of ULF waves associated with the solar wind deceleration in the Earth＇s foreshock on 6-7 April 2003 is studied using the wave telescope technique. In the satellite frame, the ULF waves are the left-handed polarized and quasi anti-parallel propagating mode, with a power peak at about 18.63mHz. The wave vector in the GSE coordinates is estimated to be k = （-4.29, 2.28, 1.21）×10^-4 km^-1, In the solar wind frame, the frequency of waves becomes - 9.39 mHz after the Doppler shift correction. The propagation direction of the waves is thus reversed and correspondingly the polarization of the waves becomes right-handed. The above-mentioned characteristics of the ULF waves in the solar wind frame indicate that the ULF waves associated with the solar wind deceleration are the Alfven-whistler waves, which have been frequently reported in both the observations and computer simulations.展开更多
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 rat...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 the radial evolution of BBFs.About 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/s.The 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 BBFs.The duration of earthward BBFs in expansion phase is larger than that in growth and recovery phases.The average durations in growth,expansion,and recovery phases are respectively 49.3,71.5,and 47.6 s.Therefore,the ratios of transports of energy of earthward BBFs in growth,expansion,and recovery phases can be estimated to be 0.51:1:0.47.Thus,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.展开更多
The distribution properties of the magnetic field in magnetotail current sheets have been explored statistically with the magnetic measurement data of the Cluster mission from June to November of the years 2001–2005....The distribution properties of the magnetic field in magnetotail current sheets have been explored statistically with the magnetic measurement data of the Cluster mission from June to November of the years 2001–2005.It is found that,on average,the strength of the magnetic field and its Bz component in the current sheet are weaker in the region close to midnight but stronger near the dawnside and duskside flanks,which implies that,in general,a thinner current sheet occurs near midnight and thicker ones near both flanks.The occurrence of tail current sheet flapping is higher on both flanks than in the midnight region,although it is most frequent in the dawn flank.Current sheets with a negative Bz component or a strong By component have a higher probability of occurring at magnetic local times of 21:00–01:00,indicating that magnetic activity,e.g.magnetic reconnection and current disruption occur more frequently there.Statistically,the probability distributions of the By component and the tilt angle of magnetic field lines in the current sheet are approximately normal distributions,and the occurrence probability of the flattened current sheet is about one third that of the normal current sheet.The magnetic field and Bz component in the current sheet mainly vary from 1 nT to 10 nT.The By component in the tail central current sheet is on average twice the IMF By at 1 AU.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 40931054 and 40523006, the National Basic Research Program of China under Grant No 2006CB806305, the National High-Tech Research and Development Program of China under Grant No 2008AA12A216, and the Specialized Research Fund for State Key Laboratories.
文摘Characteristics of ULF waves associated with the solar wind deceleration in the Earth＇s foreshock on 6-7 April 2003 is studied using the wave telescope technique. In the satellite frame, the ULF waves are the left-handed polarized and quasi anti-parallel propagating mode, with a power peak at about 18.63mHz. The wave vector in the GSE coordinates is estimated to be k = （-4.29, 2.28, 1.21）×10^-4 km^-1, In the solar wind frame, the frequency of waves becomes - 9.39 mHz after the Doppler shift correction. The propagation direction of the waves is thus reversed and correspondingly the polarization of the waves becomes right-handed. The above-mentioned characteristics of the ULF waves in the solar wind frame indicate that the ULF waves associated with the solar wind deceleration are the Alfven-whistler waves, which have been frequently reported in both the observations and computer simulations.
基金supported by National Natural Science Foundation of China (Grant Nos.40931054, 40704028 and 40523006)National Basic Research Program of China (Grant No.2006CB8062305)Specialized Research Fund for State Key Laboratories
文摘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 the radial evolution of BBFs.About 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/s.The 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 BBFs.The duration of earthward BBFs in expansion phase is larger than that in growth and recovery phases.The average durations in growth,expansion,and recovery phases are respectively 49.3,71.5,and 47.6 s.Therefore,the ratios of transports of energy of earthward BBFs in growth,expansion,and recovery phases can be estimated to be 0.51:1:0.47.Thus,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.
基金supported by the National Natural Science Foundation of China (40621003 and 40674094)the National Basic Research Program of China (2006CB806305)the Hundred Talents Program of the Chinese Academy of Sciences,and the Specialized Research Fund for State Key Laboratories
文摘The distribution properties of the magnetic field in magnetotail current sheets have been explored statistically with the magnetic measurement data of the Cluster mission from June to November of the years 2001–2005.It is found that,on average,the strength of the magnetic field and its Bz component in the current sheet are weaker in the region close to midnight but stronger near the dawnside and duskside flanks,which implies that,in general,a thinner current sheet occurs near midnight and thicker ones near both flanks.The occurrence of tail current sheet flapping is higher on both flanks than in the midnight region,although it is most frequent in the dawn flank.Current sheets with a negative Bz component or a strong By component have a higher probability of occurring at magnetic local times of 21:00–01:00,indicating that magnetic activity,e.g.magnetic reconnection and current disruption occur more frequently there.Statistically,the probability distributions of the By component and the tilt angle of magnetic field lines in the current sheet are approximately normal distributions,and the occurrence probability of the flattened current sheet is about one third that of the normal current sheet.The magnetic field and Bz component in the current sheet mainly vary from 1 nT to 10 nT.The By component in the tail central current sheet is on average twice the IMF By at 1 AU.
