Flux-rope/TCR events near the magnetotail lunar orbit （-67RE 〈 GSM X＊ 〈 -39RE） were studied using magnetic-field and plasma data measured by THEMIS B and C between January 2011 and March 2012. The aberrant coordi...Flux-rope/TCR events near the magnetotail lunar orbit （-67RE 〈 GSM X＊ 〈 -39RE） were studied using magnetic-field and plasma data measured by THEMIS B and C between January 2011 and March 2012. The aberrant coordinate GSM＊, where the X＊ axis is rotated 4° relative to GSM-X, was used to count the occurrence rate. The number ratio of earthward to tailward events was about 3：5. Moreover, the event occurrence rate distribution showed a clear dawn-dusk asymmetry distribution, with dusk-side events accounting for 57.98%. A superposed epoch analysis of the flux-rope events showed that earthward events had a shorter duration in the leading than in the trailing part. Earthward events also displayed a lower temperature and a lower flow speed than tailward events. We studied the relationship between the event occurrence rate and geomagnetic activity level even further. The occurrence rate of tailward flux-rope/TCR events increases with increasing AE-index, whereas earthward events occur mainly in the relatively quiet period of geomagnetic activity （AE - 100-300 nT）. Flux-rope/TCR events identi- fied within a 10 mm time frame were treated as belonging to a single reconnection event. By comparing the occurrence rates of earthward and tailward events along X＊, we estimated the most likely location of the near-Earth reconnection site as X＊ = -36RE.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
基金supported by the Scientific Research Foundation of Shandong Province Outstanding Young Scientist Award(Grant Nos.2013BSE27132&BS2013HZ001)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20130131120073)the National Natural Science Foundation of China(Grant Nos.41304129,41322031&41574157)
文摘Flux-rope/TCR events near the magnetotail lunar orbit （-67RE 〈 GSM X＊ 〈 -39RE） were studied using magnetic-field and plasma data measured by THEMIS B and C between January 2011 and March 2012. The aberrant coordinate GSM＊, where the X＊ axis is rotated 4° relative to GSM-X, was used to count the occurrence rate. The number ratio of earthward to tailward events was about 3：5. Moreover, the event occurrence rate distribution showed a clear dawn-dusk asymmetry distribution, with dusk-side events accounting for 57.98%. A superposed epoch analysis of the flux-rope events showed that earthward events had a shorter duration in the leading than in the trailing part. Earthward events also displayed a lower temperature and a lower flow speed than tailward events. We studied the relationship between the event occurrence rate and geomagnetic activity level even further. The occurrence rate of tailward flux-rope/TCR events increases with increasing AE-index, whereas earthward events occur mainly in the relatively quiet period of geomagnetic activity （AE - 100-300 nT）. Flux-rope/TCR events identi- fied within a 10 mm time frame were treated as belonging to a single reconnection event. By comparing the occurrence rates of earthward and tailward events along X＊, we estimated the most likely location of the near-Earth reconnection site as X＊ = -36RE.
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.
