Magnetic flux rope formation within a magnetosheath hot flow anomaly

Abstract

[1] We report observations on 1 March 2004 by the Cluster spacecraft of a hot flow anomaly (HFA) encountered in the dayside magnetosheath near Earth's bow shock. Embedded within the HFA was a magnetic flux rope with a diameter of a few thousand km, which was moving sunward and was presumably expanding. The pristine upstream solar wind seen by the ACE spacecraft contains an interplanetary current sheet favorable for the HFA formation, but shows no flux rope signatures. The properties of the flux rope, such as its slow speed, magnetic field variations, and the absence of magnetospheric electrons, are not likely to be due to magnetopause flux transfer events. These results suggest that the flux rope was created in the magnetosheath, rather than in the solar wind, in the foreshock, or on the magnetopause, through magnetic reconnection initiated in the course of the HFA development. Interestingly, energetic ($100 keV) electron fluxes were enhanced in and around this HFA-associated flux rope. The observations indicate that reconnection can occur within the magnetosheath part of HFAs and that such reconnection may play a role in electron acceleration, which is a common feature of HFAs.

MAVEN observations of a giant ionospheric flux rope near Mars resulting from interaction between the crustal and interplanetary draped magnetic fields

“…The GSR technique assumes that the structure is magnetohydrostatic and time independent [e.g., Sturrock , ; Sonnerup and Guo , ]. Previous studies extensively described how to apply the GSR technique to the magnetohydrostatic structures in space [e.g., Hau and Sonnerup , ; Hu and Sonnerup , ; Hasegawa et al , ]. Hara et al [] explained optimal treatments to apply the GSR technique to the Martian flux rope, because MAVEN detected multiple ion species.…”

MAVEN observations of magnetic flux ropes with a strong field amplitude in the Martian magnetosheath during the ICME passage on 8 March 2015

“…Recently, Hara et al [] recovered the spatial structure of a detached magnetic flux rope based on the MAVEN simultaneous plasma and magnetic field measurements. The basic procedure to apply the GSR technique is similar to previous studies [e.g., Hau and Sonnerup , ; Hu and Sonnerup , , ; Hasegawa et al , ], with the specific treatments optimized to apply the GSR technique to the Martian flux ropes detected by MAVEN extensively described in Hara et al [].…”

Estimation of the spatial structure of a detached magnetic flux rope at Mars based on simultaneous MAVEN plasma and magnetic field observations

“…Spatial integration, d ξ , can be transformed into time integration via the following relation: , where is a unit vector along the projection of − V HT onto the plane perpendicular to the invariant axis. The detailed methodology of the GSR technique is fully described in previous studies [e.g., Hau and Sonnerup , ; Hu and Sonnerup , ; Hasegawa et al , ], and we adopt the same procedure in this study.…”