Simultaneous measurements from THEMIS spacecraft, GOES11 and ground stations （Canadian Array for Realtime Investiga tions of Magnetic Activity or CARISMA, and 210 magnetic meridian or MM） on March 18, 2009 allow the...Simultaneous measurements from THEMIS spacecraft, GOES11 and ground stations （Canadian Array for Realtime Investiga tions of Magnetic Activity or CARISMA, and 210 magnetic meridian or MM） on March 18, 2009 allow the study of dynamic processes in the nearEarth magnetotail and corresponding Pi2 pulsations on the ground in great detail. Fast earthward flows along with traveling Alfv6n waves and fast mode waves in the Pi2 band were observed by three Time History of Events and Macroscale Interactions during Substorms （THEM/S） probes （P3, P4 and P5） in the nearEarth plasmasbeet. At the mid to highlatitude nightside, the CARISMA stations located near the foot points of the three probes recorded Pi2s with two periods, about 80 s after the earthward fast flows observed by the P4 probe. The longperiod Pi2 （140-150 s） belongs to the transient response Pi2 （TR Pi2）, since the travel time of the Alfv6n waves between the plasma sheet and CARISMA stations is very close to half the period of the longperiod Pi2. The shortperiod Pi2 （60-80 s） has the same period band as the perpendicular velocity of the fast flows, which indicates that it may relate to the inertial current caused by periodic braking of the earthward fast flows. The 210 MM stations located at the lowlatitude duskside also observed Pi2s with the same start time, waveform and frequency, about 120 s after the earthward fast flows. Strong poloidal oscillations are shown by GOES11 （23 MLT） and the compressional component （Bb） is highly correlated with H components of the 210 MM stations, whereas the other two components （Br and Be） are not. These results confirm that the lowlatitude Pi2s are generated by cavity mode resonance, which is driven by an impulsive broadband source in the nearEarth magnetotail.展开更多
Using Time History of Events and Macroscale Interactions during Substorms （THEMIS） observations from 2007 to 2011 tail seasons, we study the plasma properties of high speed flows （HSFs） and background plasma sheet...Using Time History of Events and Macroscale Interactions during Substorms （THEMIS） observations from 2007 to 2011 tail seasons, we study the plasma properties of high speed flows （HSFs） and background plasma sheet events （BPSs） in Earth＇s magnetotail （｜YGsM｜〈13RE, ｜ZGsM｜〈5RE, -30RE〈XrsM〈-6RE）, and their correlations with solar wind parameters. Statistical results show that the closer the HSFs and BPSs are to the Earth, the hotter they become, and the temperature increase of HSFs is larger than that of BPSs. The density and temperature ratios between HSFs and BPSs are also larger when events are closer to Earth. We also find that the best correlations between the HSFs （BPSs） density and the solar wind density occur when the solar wind density is averaged 2 （3.5） hours prior to the onset of HSFs （BPSs）. The normalized densities of both HSFs and BPSs are correlated with the interplanetary magnetic field （IMF） 0 angles （ 0 = arctan（Bz √Bx^2＋y^2 ） which are averaged 3 hours before the observation time. Further analysis indicates that both HSFs and BPSs become denser during the northward IMF period.展开更多
TC-1 observational results clearly indicate that the velocity of the flows in the near-Earth region is de- pendent on the satellite location. The flow speed decreases while satellite moves close to the Earth. The plas...TC-1 observational results clearly indicate that the velocity of the flows in the near-Earth region is de- pendent on the satellite location. The flow speed decreases while satellite moves close to the Earth. The plasma flow in the region close to the Earth tends to drift into the midnight region from the dawn and dusk region while the flow in the region away from the Earth shows an opposite drift. The obser- vational results also show that the tailward flows are mainly located in the plasma sheet boundary while the earthward flow becomes dominant in the plasma sheet. It is found that both the strong tailward and earthward flows are distributed in the region around X= -11Re, which coincides with the trigger region of the substorm onset. Hence, it may suggest that the flows are related with the trigger of the substorm onset. In addition, the BBFs coming from the mid-tail maily distributed in the region where X<-9RE and |Z|<3RE that differs from the convection.展开更多
基金supported by the National Key Basic Research Program of China (Grant No.2012CB825604)the National Natural Science Foundation of China (Grant Nos.41104093 & 41204122).
文摘Simultaneous measurements from THEMIS spacecraft, GOES11 and ground stations （Canadian Array for Realtime Investiga tions of Magnetic Activity or CARISMA, and 210 magnetic meridian or MM） on March 18, 2009 allow the study of dynamic processes in the nearEarth magnetotail and corresponding Pi2 pulsations on the ground in great detail. Fast earthward flows along with traveling Alfv6n waves and fast mode waves in the Pi2 band were observed by three Time History of Events and Macroscale Interactions during Substorms （THEM/S） probes （P3, P4 and P5） in the nearEarth plasmasbeet. At the mid to highlatitude nightside, the CARISMA stations located near the foot points of the three probes recorded Pi2s with two periods, about 80 s after the earthward fast flows observed by the P4 probe. The longperiod Pi2 （140-150 s） belongs to the transient response Pi2 （TR Pi2）, since the travel time of the Alfv6n waves between the plasma sheet and CARISMA stations is very close to half the period of the longperiod Pi2. The shortperiod Pi2 （60-80 s） has the same period band as the perpendicular velocity of the fast flows, which indicates that it may relate to the inertial current caused by periodic braking of the earthward fast flows. The 210 MM stations located at the lowlatitude duskside also observed Pi2s with the same start time, waveform and frequency, about 120 s after the earthward fast flows. Strong poloidal oscillations are shown by GOES11 （23 MLT） and the compressional component （Bb） is highly correlated with H components of the 210 MM stations, whereas the other two components （Br and Be） are not. These results confirm that the lowlatitude Pi2s are generated by cavity mode resonance, which is driven by an impulsive broadband source in the nearEarth magnetotail.
基金National Natural Science Foundation of China (Grant Nos. 41322031, 41031065 & 41574157)the Shandong Province Outstanding Young Scientist Award (Grant No. 2013BSE27132)+2 种基金the Research Fund for the Doctoral Program of Higher Education (Grant No. 20130131120073)the program for New Century Excellent Talents in University (Grant No. NCET-12-0332)State Key Laboratories of Space Weather
文摘Using Time History of Events and Macroscale Interactions during Substorms （THEMIS） observations from 2007 to 2011 tail seasons, we study the plasma properties of high speed flows （HSFs） and background plasma sheet events （BPSs） in Earth＇s magnetotail （｜YGsM｜〈13RE, ｜ZGsM｜〈5RE, -30RE〈XrsM〈-6RE）, and their correlations with solar wind parameters. Statistical results show that the closer the HSFs and BPSs are to the Earth, the hotter they become, and the temperature increase of HSFs is larger than that of BPSs. The density and temperature ratios between HSFs and BPSs are also larger when events are closer to Earth. We also find that the best correlations between the HSFs （BPSs） density and the solar wind density occur when the solar wind density is averaged 2 （3.5） hours prior to the onset of HSFs （BPSs）. The normalized densities of both HSFs and BPSs are correlated with the interplanetary magnetic field （IMF） 0 angles （ 0 = arctan（Bz √Bx^2＋y^2 ） which are averaged 3 hours before the observation time. Further analysis indicates that both HSFs and BPSs become denser during the northward IMF period.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40390150, 40536030 and 40674094)
文摘TC-1 observational results clearly indicate that the velocity of the flows in the near-Earth region is de- pendent on the satellite location. The flow speed decreases while satellite moves close to the Earth. The plasma flow in the region close to the Earth tends to drift into the midnight region from the dawn and dusk region while the flow in the region away from the Earth shows an opposite drift. The obser- vational results also show that the tailward flows are mainly located in the plasma sheet boundary while the earthward flow becomes dominant in the plasma sheet. It is found that both the strong tailward and earthward flows are distributed in the region around X= -11Re, which coincides with the trigger region of the substorm onset. Hence, it may suggest that the flows are related with the trigger of the substorm onset. In addition, the BBFs coming from the mid-tail maily distributed in the region where X<-9RE and |Z|<3RE that differs from the convection.
