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Cao J.B.,Beihang University | Cao J.B.,Key Laboratory for Space Weather CSSAR | Wang Z.Q.,Key Laboratory for Space Weather CSSAR | Wang Z.Q.,University of Chinese Academy of Sciences | And 2 more authors.
Science China Technological Sciences | Year: 2012

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. © Science China Press and Springer-Verlag Berlin Heidelberg 2012.


Cao J.B.,Beihang University | Cao J.B.,Key Laboratory for Space Weather CSSAR | Ding W.Z.,Key Laboratory for Space Weather CSSAR | Reme H.,Roche Holding AG | And 6 more authors.
Annales Geophysicae | Year: 2011

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 in near equatorial orbits outside 6.6 RE. In this paper, we used the ion data recorded by TC-1 from 2004 to 2006 to study the distribution of inner boundary of ion plasma sheet (IBIPS) and for the first time show the observational distribution of IBIPS in the equatorial plane. The IBIPS has a dawn-dusk asymmetry, being farthest to the Earth in the 06:00 08:00 LT bin and closest to the Earth in the 18:00-20:00 LT bin. Besides, the IBIPS has also a day-night asymmetry, which may be due to the fact that the ions on the dayside are exposed more time to loss mechanisms on their drift paths. The radial distance of IBIPS decrease generally with the increase of Kp index. The mean radial distance of IBIPS is basically larger than 6.6 RE during quiet times and smaller than 6.6 RE during active times. When the strength of convection electric field increases, the inward shift of IBIPS is most significant on the night side (22:00-02:00 LT). For Kp≤0+, only 16% of IBIPSs penetrate inside the geosynchronous orbit. For 2≤Kp < 3+, however, 70% of IBIPSs penetrate inside the geosynchronous orbit. The IBIPS has weak correlations with the AE and Dst indexes. The average correlation coefficient between Ri and Kp is -0.58 while the correlation coefficient between Ri and AE/Dst is only -0.29/0.17. The correlation coefficients are local time dependent. Particularly, Ri and Kp are highly correlated (r=-0.72) in the night sector, meaning that the radial distance of IBIPS Ri in the night sector has the good response to the Kp index These observations indicate that Kp plays a key role in determining the position of IBIPS. © 2011 Author(s).

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