Radial distribution of magnetic field in earth magnetotail current sheet
【摘要】：Knowing the magnetic field distribution in the magnetotail current sheet(CS) is essential for exploring magnetotail dynamics.In this study,using a joint dataset of Cluster/TC-1,the radial profile of the magnetic field in the magnetotail CS with radial distances covering 8r20R_E under different geomagnetic activity states(i.e.,AE≤100 nT for quiet intervals while AE 100 nT for active times)and solar wind parameters are statistically surveyed.Our new findings demonstrate that,independent of the activity state,the field strength and B_z component(GSM coordinates) start the monotonic increase prominently as r decreases down to ~11.5R_E,which means the dipole field starts to make a significant contribution from there.At least in the surveyed radial range,the B_z component is found to be weaker in the midnight and dusk sectors than that in the dawn sector,displaying a dawn-dusk asymmetry.The occurrence rate of negative B_z in active times also exhibits a similar asymmetric distribution,which implies active dynamics may occur more frequently at midnight and dusk flank.In comparison with that in quiet intervals,several features can be seen in active times:(1) a local B_z minimum between10.5r 12.5R_E is found in the dusk region,(2) the B_z component around the midnight region is generally stronger and experiences larger fluctuations,and(3) a sharp positive/negative-excursion of the B_y component occurs at the dawn/dusk flank regions inside r10R_E.The response to solar wind parameters revealed that the B_z component is generally stronger under higher dynamic pressure(P_(dy) 5 nPa),which may support the dawn-dusk squeezing effect as presented by Miyashita et al.(2010).The CS B_y is generally correlated with the interplanetary magnetic field(IMF) B_y component,and the correlation quality is found to be better with higher penetration coefficient(the ratio of CS B_y to IMF B_y) when IMF B_z is positive.The implications of the present results are discussed.
【作者单位】：Key Laboratory of Earth and Planetary Physics,Institute of Geology and Geophysics,Chinese Academy of Sciences Beijing National Observatory of Space Environment,Institute of Geology and Geophysics,Chinese Academy of Sciences State Key Laboratory of Space Weather,Center for Space Science and Applied Research,Chinese Academy of Sciences Space Research Institute Space Research Institute,Austrian Academy of Sciences Rutherford Appleton Laboratory 【基金】：supported by the Chinese Academy of Sciences(KZZD-EW-01-2)
National Basic Research Program of China(973 Program)Grants2011CB811404 and 2011CB811405
the National Natural Science Foundation of China Grants 41104114,41374180,41321003,40974101,41131066 and 41211120182
China Postdoctoral Science Foundation Funded Project 2012T50132
the Research Fund for the State Key Laboratory of Lithospheric Evolution 【分类号】：