Field aligned current （FAC） distribution in the plasma sheet boundary layers （PSBLs） in the magnetotail is studied statistically by analysing magnetic field data from the Cluster 4-point measurements. The results ...Field aligned current （FAC） distribution in the plasma sheet boundary layers （PSBLs） in the magnetotail is studied statistically by analysing magnetic field data from the Cluster 4-point measurements. The results show that the FAC distribution on the dusk side is not the same as that on the dawn side in the magnetotail. On the each side earthward and tailward, FA C occurrences are different; occurrence and average current density of FA Cs in the northern hemisphere are different from those in the southern hemisphere. This implies that the FACs have dusk-dawn side asymmetry, polarity asymmetry and inter hemisphere difference in the magnetotail. The present results give a good observation evidence for study on the FAC mechanism.展开更多
We have studied 172 field-aligned currents （FACs） cases observed by the ClusterlI satellites when they crossed the plasma sheet boundary layer （PSBL） in the magnetotail from July to October 2001. We mainly analyze...We have studied 172 field-aligned currents （FACs） cases observed by the ClusterlI satellites when they crossed the plasma sheet boundary layer （PSBL） in the magnetotail from July to October 2001. We mainly analyzed the relationship between the characteristic of FACs at the PSBL in magnetotail and the Kp index. The main results indicated the followings： 1） In the different geomagnetic activity levels, the relative occurrence of FACs in PSBL increased monotonically with geomagnetic activity. 2） The density of FACs in PSBL increased monotonically with Kp index. In the storm main phase, the density of FACs increased dramatically, the maximum FACs approximately equaled 19.05 nA m-2 while Kp equaled 5.3） The variation of FACs density in PSBL was consistent with the variation of the Kp index. However, when AE〈800 nT, FACs density in PSBL increased with increasing AE, and when AE〉800 nT, it decreased with increasing AE. Therefore, our results suggested that the FACs density in PSBL had a closer correlation with Kp index.展开更多
Cold ions of plasmaspheric origin have been observed to abundantly appear in the magnetospheric side of the Earth's magnetopause. These cold ions could affect the magnetic reconnection processes at the magnetopaus...Cold ions of plasmaspheric origin have been observed to abundantly appear in the magnetospheric side of the Earth's magnetopause. These cold ions could affect the magnetic reconnection processes at the magnetopause by changing the Alfvén velocity and the reconnection rate, while they could also be heated in the reconnection layer during the ongoing reconnections. We report in situ observations from a partially crossing of a reconnection layer near the subsolar magnetopause. During this crossing, step-like accelerating processes of the cold ions were clearly observed, suggesting that the inflow cold ions may be separately accelerated by the rotation discontinuity and slow shock inside the reconnection layer.展开更多
Using coordinated observations from the Cluster,DMSP and ESR radar,high-altitude cusp was investigated for a time period characterized by four fast reversals of the IMF BZ.On February 12,2003,Cluster was flying sunwar...Using coordinated observations from the Cluster,DMSP and ESR radar,high-altitude cusp was investigated for a time period characterized by four fast reversals of the IMF BZ.On February 12,2003,Cluster was flying sunward at duskside over the Northern Hemisphere,across the high-altitude northern cusp twice.Both the two crossings are during steady northward IMF interval,whereas ion fluxes detected during the time period are quite different.The cusp in the first crossing is a "typical" northward-IMF one,with short-lived ion injections of evident "reversed" dispersion signatures.In the second crossing,however,the cusp appears to be a region reminiscent of the Stagnant Exterior Cusp (SEC).In addition,evident upward-flowing O+ ion bursts,possibly original from polar ionosphere,are also detected during the second cusp crossing,together with enhancement of trapped magnetospheric-like electron fluxes.We suggest that the SEC-like cusp is likely on newly closed field lines,which were first reconnected (being opened) at low latitudes and later reconnected again (being closed) poleward of the northern cusp.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 40674091, 40621003 and 40874084, and the Specialized Research Fund for State Key Laboratories.
文摘Field aligned current （FAC） distribution in the plasma sheet boundary layers （PSBLs） in the magnetotail is studied statistically by analysing magnetic field data from the Cluster 4-point measurements. The results show that the FAC distribution on the dusk side is not the same as that on the dawn side in the magnetotail. On the each side earthward and tailward, FA C occurrences are different; occurrence and average current density of FA Cs in the northern hemisphere are different from those in the southern hemisphere. This implies that the FACs have dusk-dawn side asymmetry, polarity asymmetry and inter hemisphere difference in the magnetotail. The present results give a good observation evidence for study on the FAC mechanism.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40804031, 41074114, 40921063)the Specialized Research Fund for State Key Laboratories
文摘We have studied 172 field-aligned currents （FACs） cases observed by the ClusterlI satellites when they crossed the plasma sheet boundary layer （PSBL） in the magnetotail from July to October 2001. We mainly analyzed the relationship between the characteristic of FACs at the PSBL in magnetotail and the Kp index. The main results indicated the followings： 1） In the different geomagnetic activity levels, the relative occurrence of FACs in PSBL increased monotonically with geomagnetic activity. 2） The density of FACs in PSBL increased monotonically with Kp index. In the storm main phase, the density of FACs increased dramatically, the maximum FACs approximately equaled 19.05 nA m-2 while Kp equaled 5.3） The variation of FACs density in PSBL was consistent with the variation of the Kp index. However, when AE〈800 nT, FACs density in PSBL increased with increasing AE, and when AE〉800 nT, it decreased with increasing AE. Therefore, our results suggested that the FACs density in PSBL had a closer correlation with Kp index.
基金supported by the National Natural Science Foundation of China(41574138,41604139)the Shandong Provincial Natural Science Foundation(JQ201412)+5 种基金the Chinese Meridian ProjectReading University was supported by STFC consolidated(ST/M000885/1)The Norwegian contribution was supported by the Research Council of Norway(230996.S.R.Z.)support from the U.S.NASA LWS Project(NNX15AB83G)the U.S.Do D MURI Project(ONR15-FOA-0011)supported by the U.S.NSF Geospace Facility program under an agreement AGS-1242204 with Massachusetts Institute of Technology
文摘Cold ions of plasmaspheric origin have been observed to abundantly appear in the magnetospheric side of the Earth's magnetopause. These cold ions could affect the magnetic reconnection processes at the magnetopause by changing the Alfvén velocity and the reconnection rate, while they could also be heated in the reconnection layer during the ongoing reconnections. We report in situ observations from a partially crossing of a reconnection layer near the subsolar magnetopause. During this crossing, step-like accelerating processes of the cold ions were clearly observed, suggesting that the inflow cold ions may be separately accelerated by the rotation discontinuity and slow shock inside the reconnection layer.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40874079)the Ministry of Science and Technology of China (Grant No. 2006BAB18B06)
文摘Using coordinated observations from the Cluster,DMSP and ESR radar,high-altitude cusp was investigated for a time period characterized by four fast reversals of the IMF BZ.On February 12,2003,Cluster was flying sunward at duskside over the Northern Hemisphere,across the high-altitude northern cusp twice.Both the two crossings are during steady northward IMF interval,whereas ion fluxes detected during the time period are quite different.The cusp in the first crossing is a "typical" northward-IMF one,with short-lived ion injections of evident "reversed" dispersion signatures.In the second crossing,however,the cusp appears to be a region reminiscent of the Stagnant Exterior Cusp (SEC).In addition,evident upward-flowing O+ ion bursts,possibly original from polar ionosphere,are also detected during the second cusp crossing,together with enhancement of trapped magnetospheric-like electron fluxes.We suggest that the SEC-like cusp is likely on newly closed field lines,which were first reconnected (being opened) at low latitudes and later reconnected again (being closed) poleward of the northern cusp.
