Influences of the interplanetary magnetic field clock angle and cone angle on the field‐aligned currents in the magnetotail

Abstract

[1] The influences of the interplanetary magnetic field (IMF) cone angle θ and clock angle φ on the field-aligned currents (FACs) at the plasma sheet boundary layers (PSBLs) have been investigated using Cluster Data. The FAC occurrence increases monotonically with IMF cone angle and has two peaks at À90°and +110°clock angle, respectively. The peak at +110°is distinctly larger than that at À90°. Overall, there are more FACs between 0°< φ < 180°, indicating that FACs occurrence is closely associated with duskward IMF. More FACs occur when 90°< |φ| < 180°, implying that FAC is closely associated with southward IMF. The large FAC densities occur when 60°< |φ| < 120°. The density also has two peaks and the peak at +90°clock angle (duskward IMF) is larger than that at À90°(dawnward IMF). These results indicate that the IMF influence on the FACs is from all IMF components and not only from a single component. Citation: Cheng, Z. W., J. K. Shi, M. Dunlop, and Z. X. Liu (2013), Influences of the interplanetary magnetic field clock angle and cone angle on the field-aligned currents in the magnetotail, Geophys. Res. Lett., 40,[5355][5356][5357][5358][5359]

Influence of the IMF Cone Angle on Invariant Latitudes of Polar Region Footprints of FACs in the Magnetotail: Cluster Observation

“…With the IMF cone angle increasing, the density of the FACs also increased. This is consistent with the result obtained by Cheng et al (). The large FAC cases occur at lower ILATs (below 71°), and they mainly occur when θ > 60°.…”

“…In this study, the boundaries of the footprints of the FACs in the magnetotail seemed consistent with a variation of the boundaries of the auroral oval. The IMF cone angle can control the efficiency of magnetic reconnection both at the magnetopause and in the magnetotail (Cheng et al, ; Scurry et al, ; Y. Wang, Elphic, et al, ). The observed dependence of geomagnetic activity on the orientation of the IMF is expected as a consequence of magnetic reconnection.…”

“…In the magnetotail, both the IMF cone angle and clock angle are important factors and have great influence on the FACs. Cheng et al () found that the FAC occurrence in the magnetotail increases monotonically with the IMF cone angle. The FAC is a large‐scale phenomenon in the magnetosphere‐ionosphere system.…”

Environmental Conditions During the Reported Charging Anomalies of the Two Geosynchronous Satellites: Telstar 401 and Galaxy 15

“…There are several previous studies on the influence of one of the components of the IMF in the entrance of energy from the solar wind to the magnetosphere‐ionosphere system and on the asymmetries associated with the relevant role played by any IMF component by minimizing the role of the others (Belenkaya et al, ; Chakrabarty et al, ; Cheng et al, , ; Liou et al, ; Ostgaard et al, , ; Tenfjord et al, ; Wing et al, ). However, the IMF influence on the FACs in the magnetotail should be a combined contribution of all IMF components and not only from a single one (Cheng et al, ).…”

“…From the sign and the magnitude of the IMF components in this time interval, the asymmetry angle γ, defined as tan (γ) = −By/Bx (Belenkaya et al, ), was positive indicating a significant shift (≈4–5 hr) of the magnetospheric field lines, which displaced the FAC current circuit from midnight to dawn. Additionally, the cone angle θ, defined as cos (θ) = |Bx|/B (Cheng et al, ), was larger than 80°. This cone angle is well related to the FAC occurrence rate, especially for Northern Bz IMF conditions, keeping this rate high when the angle is high, as in this case.…”