In solar wind-magnetosphere-ionosphere interactions, the large-scale FAC plays a crucial role in transferring the solar wind momentum and energy to magnetosphere and ionosphere. The large-scale (reaching from the magnetotail to the ionosphere) FACs are involved in many important physical processes, including field-aligned particle acceleration (Choy et al., 1971 Morooka et al., 2004 Shi et al., 2014), magnetic reconnection in the magnetotail (Hones, 1979 Ma & Otto, 2013 Scholer & Otto, 1991), development of the substorm current wedge (Hesse & Birn, 1991 Pytte et al., 1976), and auroral activity (Elphic et al., 1998 Xiong et al., 2014). Key Pointsįield-aligned currents (FACs) were detected by satellites for the first time in the 1960s (Cummings & Dessler, 1967 Zmuda et al., 1966), and they have been observed at both low (Iijima & Potemra, 1978) and high (Frank, 1981) altitudes in different regions in geospace. This is the first time a correlation between FAC footprints in the polar region and IMF cone angles has been determined. This is because the poleward boundary movement is limited by an enhanced lobe magnetic flux. There is almost no correlation between the poleward boundary and the IMF cone angle for both northward and southward IMF. The equatorward boundary of the FAC footprints in the polar region decreases with increasing IMF cone angle (and has a better correlation for northward IMF), which shows that the IMF cone angle plays an important controlling role in FAC distributions in the magnetosphere-ionosphere coupling system. The footprints of the large FAC (>10 nA/m 2) cases are within invariant latitudes 60°, which implies that the footprints of the large FACs mainly expand equatorward with large IMF cone angle. The results show that there are almost no FACs when the IMF cone angle is less than 10°, and there are indications of the FACs in the plasma sheet boundary layers being weak under the radial IMF conditions. We performed a statistical study of 542 FAC cases observed by the four Cluster spacecraft in the Northern Hemisphere. NASA Space Physics Data Facility.The influence of the interplanetary magnetic field (IMF) cone angle θ (the angle between the IMF direction and the Sun-Earth line) on the invariant latitudes of the footprints of the field-aligned currents (FACs) in the magnetotail has been investigated. Parker Solar Probe (PSP) Merged Magnetic Field, Plasma, and Ephemeris, Hourly Data.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |