Reconstruction of a bipolar magnetic signature in an earthward jet in the tail: Flux rope or 3D guide‐field reconnection?

Hasegawa, H.; Nakamura, R.; Fujimoto, M.; Сергеев, В. А.; Lucek, E.; Rème, H.; Khotyaintsev, Yuri V.

doi:10.1029/2007ja012492

Cited by 39 publications

(47 citation statements)

References 31 publications

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“…The strong core field B y of these structures can be explained by three-dimensional (3-D) guide-field reconnection as demonstrated in magnetohydrodynamic (MHD) simulations by Shirataka et al (2006). Later, Hasegawa et al (2007) used the results of these MHD simulations for GS reconstruction analysis and showed that this technique can reconstruct flux ropes in the configurations without flux ropes being actually present. The latter means that one should be cautious when interpreting GS reconstruction results.…”

Section: Discussionmentioning

confidence: 99%

“…The latter means that one should be cautious when interpreting GS reconstruction results. Hasegawa et al (2007) summed up a guideline that can be used to distinguish flux ropes from a 3-D guide-field reconnection configuration. According to that guideline, the feature not typical for flux ropes is the presence of perpendicular velocity components in the HT frame, which is an indication of temporal variation of the structure, and plasma pressure enhancement in the leading part of the structure.…”

Section: Discussionmentioning

confidence: 99%

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Dipolarization fronts in the near-Earth space and substorm dynamics

et al. 2015

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Abstract. During magnetospheric substorms and plasma transport in the Earth's magnetotail various magnetic structures can be detected. Dipolarization fronts and flux ropes are the most prominent structures characteristic for substorm dynamics. However, they are treated as separate magnetotail features independent of each other. In this paper, we analyze a number of dipolarization fronts observed by the THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft at different geocentric distances by applying the magnetohydrostatic Grad-Shafranov (GS) reconstruction technique. Our analysis shows that there is a possibility of dipolarization fronts to originate from highly dissipated flux ropes which are in the late stage of their evolution, subjected to a continuous magnetic deterioration due to the reconnection process. These results may improve our understanding of magnetoplasma processes in Earth's magnetotail.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Dipolarization fronts in the near-Earth space and substorm dynamics

et al. 2015

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“…However, we do not rely on the topological property of the recovered field to infer if single or multiple X-lines were involved. This is because if the structure has some threedimensionality, the GSR method may lead to closed field loops in the 2D map even when there is in fact only single X-line [Hasegawa et al, 2007].…”

Section: Observations and Analysismentioning

confidence: 99%

Evidence for a flux transfer event generated by multiple X‐line reconnection at the magnetopause

Hasegawa¹,

Wang

Dunlop

et al. 2010

Geophysical Research Letters

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134

176

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[1] Magnetic flux transfer events (FTEs) are signatures of unsteady magnetic reconnection, often observed at planetary magnetopauses. Their generation mechanism, a key ingredient determining how they regulate the transfer of solar wind energy into magnetospheres, is still largely unknown. We report THEMIS spacecraft observations on 2007-06-14 of an FTE generated by multiple X-line reconnection at the dayside magnetopause. The evidence consists of (1) two oppositely-directed ion jets converging toward the FTE that was slowly moving southward, (2) the cross-section of the FTE core being elongated along the magnetopause normal, probably squeezed by the oppositely-directed jets, and (3) bidirectional field-aligned fluxes of energetic electrons in the magnetosheath, indicating reconnection on both sides of the FTE. The observations agree well with a global magnetohydrodynamic model of the FTE generation under large geomagnetic dipole tilt, which implies the efficiency of magnetic flux transport into the magnetotail being lower for larger dipole tilt. Citation: Hasegawa, H., et al. (2010), Evidence for a flux transfer event generated by multiple X-line reconnection at the magnetopause, Geophys. Res. Lett., 37, L16101,

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“…The first FR was found by Amm et al (2006) to be tilted by ∼29 • from the GSM y-axis as seen from the +z-direction. The second signature, on the other hand, was discovered by Hasegawa et al (2007) to have been produced by a rather round FR oriented mainly in the y-direction, with a relaxed, approximately minimum-energy configuration. The tilt from the GSM y-axis as seen from the +z-direction was only ∼4 • .…”

Section: Auroral Emissionsmentioning

confidence: 99%

“…They suggested that this region of downward current, together with a trailing region of upward current further southwestward, might correspond to the ends of the flux rope. Recently, Hasegawa et al (2007) applied the Grad-Shafranov (GS, Sonnerup et al, 2006) reconstruction to the second FR. They deduced that the signature was most likely caused by a FR as opposed to, for instance, 3-D reconnection.…”

Section: Introductionmentioning

confidence: 99%

Ionospheric signatures during a magnetospheric flux rope event

et al. 2008

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Abstract. On 13 August 2002, during a substorm, Cluster encountered two earthward moving flux ropes (FR) in the central magnetotail. The first FR was observed during the expansion phase of the substorm, and the second FR during the recovery phase. In the conjugate ionospheric region in Northern Fennoscandia, the ionospheric equivalent currents were observed by the MIRACLE network and the auroral evolution was monitored by the Wideband Imaging Camera (WIC) on-board the IMAGE satellite. Extending the study of Amm et al. (2006), we examine and compare the possible ionospheric signatures associated with the two FRs. Amm et al. studied the first event in detail and found that the ionospheric footprint of Cluster coincided with a region of downward field-aligned current. They suggested that this region of downward current, together with a trailing region of upward current further southwestward, might correspond to the ends of the FR. Unlike during the first FR, however, we do not see any clear ionospheric features associated with the second one. In the GSM xy-plane, the first flux rope axis was tilted with respect to the y-direction by 29 • , while the second flux rope axis was almost aligned in the y-direction, with an angle of 4 • only. It is possible that due to the length and orientation of the second FR, any ionospheric signatures were simply mapped outside the region covered by the ground-based instruments. We suggest that the ground signatures of a FR depend on the orientation and the length of the structure.

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Reconstruction of a bipolar magnetic signature in an earthward jet in the tail: Flux rope or 3D guide‐field reconnection?

Cited by 39 publications

References 31 publications

Dipolarization fronts in the near-Earth space and substorm dynamics

Dipolarization fronts in the near-Earth space and substorm dynamics

Evidence for a flux transfer event generated by multiple X‐line reconnection at the magnetopause

Ionospheric signatures during a magnetospheric flux rope event

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