| Popis: |
The interaction of the solar wind with the Earth’s magnetosphere can result in various disturbance phenomena inside the magnetosphere, such as the density, occurrence, and distribution of the field-aligned currents (FACs) in the magnetosphere-ionosphere system. The FACs take an important role in the magnetosphere - ionosphere coupling and have been investigated for many decades. However, it’s response to the solar wind and IMF still needs to be further studied. In this study, we statistically investigate the influence of the solar wind dynamic pressure (SW Pdyn) on the FACs in the magnetotail based on 1492 FAC cases occurring from July to October in 2001 and 2004, which covers 117 Cluster spacecraft crossings of plasma sheet boundary layer (PSBL). The FAC density in the magnetotail is derived from the magnetic field data with the four-point measurement of Cluster and the SW Pdyn is derived from ACE data. It was confirmed that the magnetotail FAC density depended on the solar wind dynamic pressure during both magnetic storm and non-storm time, and the FAC density was much stronger with intense SW Pdyn during storm time. The statistical results show that the FAC occurrence increases monotonically with SW Pdyn in the three levels (weak: SW Pdyndyn>5 nPa). The FAC density increases with increasing SW Pdyn, while its footprint (invariant latitude, ILAT) in the polar region decreases with increasing SW Pdyn. Also, the FAC in the magnetotail response to SW Pdyn has a north-south hemispheric asymmetry. The correlation of FAC density with SW Pdyn is better in the Northern Hemisphere, while the correlation of the footprint position with SW Pdyn is better in the Southern Hemisphere. Furthermore, the influences of the solar wind core angle and clock angle on the FAC density, occurrence, and distribution are also shown in this presentation. The concerned mechanisms for our results are analyzed and discussed. |
