A Magnetohydrodynamic Modeling of the Interchange Cycle for Oblique Northward Interplanetary Magnetic Field

Watanabe, Masakazu; Fujita, Shigeru; Tanaka, Takashi; Kubota, Yasubumi; Shinagawa, Hiroyuki; Murata, Ken T.

doi:10.1002/2017ja024468

Cited by 8 publications

(41 citation statements)

References 34 publications

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“…There have been previous simulations of nonlobe reconnection at the magnetopause (e.g., Watanabe et al, ). In addition, there have been previous observations of nonlobe reconnection at the magnetopause.…”

Section: Discussionmentioning

confidence: 99%

“…In particular, the field lines inside the magnetosphere are connected to the ionosphere in the northern hemisphere for nonlobe reconnection and are completely disconnected from the Earth for lobe reconnection. There have been simulations (Vennerstrom et al, ; Watanabe et al, ) and observations (Onsager et al, ) arguing for nonlobe reconnection for northward IMF.…”

Section: Introduction To Reconnection Topologies For Northward Imfmentioning

confidence: 99%

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Nonlobe Reconnection at the Earth's Magnetopause for Northward IMF

et al. 2018

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Under northward interplanetary magnetic field conditions, magnetic reconnection at the Earth's magnetopause is usually thought to operate through the merging of magnetosheath magnetic field lines and open magnetic field lines from the magnetospheric lobe. However, reconnection also occurs between magnetosheath field lines and closed magnetic field lines in the magnetosphere. Under certain conditions, this nonlobe field line reconnection has distinct plasma and magnetic field signatures that distinguish it from reconnection of lobe field lines. A survey of these conditions suggests that nonlobe reconnection at the Earth's magnetopause may be common even for relatively strong northward IMF.Plain Language Summary Magnetic reconnection interconnects magnetic field lines across a current sheet like that at the Earth's magnetopause or like that in the solar corona. This paper describes a type of interconnection of magnetic field lines at the magnetopause that was first reported for the solar corona. It appears that this type of reconnection is fairly common at the magnetopause. The different topology of this reconnection suggests a different type of interaction between the magnetic field lines in the solar wind and the field lines of the Earth.Lobe reconnection is not the only magnetic topology possible when the IMF is northward. Cowley (1983) suggested several different magnetic topologies that may result from reconnection when the IMF is northward. Two of these topologies are illustrated in Figure 1. The topology on the left-hand side results from lobe reconnection. The Sun is to the left, and a magnetosheath field line, 1, convecting toward the magnetopause reconnects in the southern hemisphere with a lobe field line, 2, poleward of the cusp. A lobe field line is defined, prior to reconnection, as a field line with one foot in the ionosphere and the other far downtail and essentially not connected to the Earth. After reconnection, the resulting open field line, 1 0 , still has one FUSELIER ET AL. 8275

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Section: Discussionmentioning

confidence: 99%

Section: Introduction To Reconnection Topologies For Northward Imfmentioning

confidence: 99%

Nonlobe Reconnection at the Earth's Magnetopause for Northward IMF

et al. 2018

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“…At the beginning ( T = −86 min) the IMF is still northward, and the northern ionosphere consists of two regions, the C region and the NNO region. Structures of the FAC and ionospheric convection at this time are analyzed in detail in Tanaka, Obara, et al () and Watanabe et al (). The distribution of the FAC reproduces the horse collar structure and the Sun‐aligned arc.…”

Section: Development Of the Open‐closed Boundary In The Ionospherementioning

confidence: 99%

Development of Magnetic Topology During the Growth Phase of the Substorm Inducing the Onset of the Near‐Earth Neutral Line

et al. 2019

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The transition of magnetic topology is analyzed during the substorm. During the growth phase in the polar ionosphere, magnetic fields consist of three categories: closed magnetic field, open magnetic field leading to the northward interplanetary magnetic field (IMF), and open field leading to the southward IMF. While the open magnetic field region leading to the southward IMF expands consistently during the growth phase, the ionospheric onset starts inside the closed field line region. There should be triple points where three kinds of magnetic field coexist in the ionosphere. Connected to the triple points, complex magnetic topologies appear in the magnetosphere. There occur definitive changes in the global magnetic topology such as retreat of cusp nulls generated under the northward IMF, generation of plasma sheet magnetic fields with reverse curvature, generation of bifurcation areas on the magnetopause, formation of new dayside nulls, development of null lines on the flank, and generation of bifurcation areas (group of nulls) on the magnetopause. During the late growth phase, divergence Vx flow is excited in the central plasma sheet associated with the appearance of reverse curvature. The plasma sheet reconnection starts 5 min before the ionospheric onset from a localized area at X = −17.5 Re due to the reduction of the normal component Bz caused by divergence Vx flow. It occurs in the residual magnetic structure formed under the northward IMF as a three‐dimensional reconnection with a guide field By. The resulting two‐turn coil of magnetic field forms a plasmoid, which is ejected downtail.

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“…On the one hand, the reconnection drives convection, and at the same time convection transports and deforms the magnetic field configuration through the frozen‐in principle. In a quasi‐steady magnetosphere, magnetic field lines newly reformed by the reconnection are balancing with magnetic field lines transported out by convection (Watanabe et al, ). However, due to the switching of the solar wind or the deformation limit of the magnetic field structure, it sometimes becomes necessary to change the topology and null distribution.…”

Section: Introductionmentioning

confidence: 99%

“…Whereas the topology of the solar wind‐magnetosphere‐ionosphere system can be investigated from Figure , the influence of dynamics cannot be evaluated only from Figure . By the global MHD simulation, however, it is possible not only to reproduce the topology under a certain condition but also to evaluate the development of topology induced from the dynamics (Watanabe et al, ). In this paper, we would like to relate the developments of dynamics and global magnetic topology with auroral observations through distributions of the FAC and closed magnetic field lines.…”

Section: Introductionmentioning

confidence: 99%

Cooperatives Roles of Dynamics and Topology in Generating the Magnetosphere‐Ionosphere Disturbances: Case of the Theta Aurora

et al. 2018

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To understand the magnetosphere‐ionosphere (M‐I) disturbances, it is necessary to know the change in the null‐separator structure along with the development of convection. The present paper explains this proposition by taking the case of the theta aurora that occurs after the switch of interplanetary magnetic field By and reveals auroral development inside the polar cap. The interplanetary magnetic field change is followed by the reformation of the null‐separator structure to cause a convection transient and a successive deformation of separatrices inside the magnetosphere, where separatrices separate the space into different volumes that include different types of magnetic field lines, and intersections of separatrices form separators that connect nulls. By the reconnection on the separator, energy inflow occurs from the solar wind to the magnetosphere. Convection driven by this energy transports nulls. In the case of theta aurora, two new nulls on the dayside coexist with two old nulls carried toward the tail by convection. Each set of nulls generates two open‐closed boundaries (separatrices) bounded by separators. Thus, open‐closed boundaries are divide into four parts. Separatrices generated by different sets partially become side by side near the nightside stem limes. The theta aurora is generated at the area corresponding to the low‐latitude side with respect to both of two boundaries. Thus, the occurrence of the theta aurora is a natural consequence of a transition in the null‐separator structure. The present example indicates that the global structure of the magnetosphere is almost decided from the skeleton of nulls.

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A Magnetohydrodynamic Modeling of the Interchange Cycle for Oblique Northward Interplanetary Magnetic Field

Cited by 8 publications

References 34 publications

Nonlobe Reconnection at the Earth's Magnetopause for Northward IMF

Nonlobe Reconnection at the Earth's Magnetopause for Northward IMF

Development of Magnetic Topology During the Growth Phase of the Substorm Inducing the Onset of the Near‐Earth Neutral Line

Cooperatives Roles of Dynamics and Topology in Generating the Magnetosphere‐Ionosphere Disturbances: Case of the Theta Aurora

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