Dawn‐Dusk Confinement of Magnetic Reconnection Site in the Near‐Earth Magnetotail and Its Implication for Dipolarization and Substorm Current System

Nagai, T.; Shinohara, I.

doi:10.1029/2021ja029691

Cited by 8 publications

(20 citation statements)

References 44 publications

(109 reference statements)

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“…The ground stations FRN, BOU, BSL, and FRD were used for most cases. Then, we identify a positive bay and its zero D deflection meridian according to the method adopted by Nagai and Shinohara (2021). Therefore, we use well-isolated events, and we take the first onset when there are successive onsets.…”

Section: Mcpherronmentioning

confidence: 99%

“…The Geotail spacecraft was used to conduct magnetic field and plasma observations in the plasma sheet for the period of 1998-2020. All magnetic reconnection events used in this study are the same as those selected by Nagai and Shinohara (2021). Any magnetic reconnection event that met the selection criteria by Nagai and Shinohara (2021) was not obtained in 2020.…”

Section: Datamentioning

confidence: 99%

“…This value, which is expressed as VBs in this study, is similar to that of the solar wind electric field; however, it can more effectively express the energy input from the solar wind to the magnetosphere through dayside magnetic reconnection. We examined various solar wind parameters during the magnetic reconnection events studied by Nagai and Shinohara (2021). The solar wind energy input manifests the most prominent characteristics for magnetic reconnection in the postmidnight sector.…”

Section: Introductionmentioning

confidence: 99%

“…Nagai and Shinohara (2021) reported distribution of in situ magnetic reconnection observations in the near‐Earth magnetotail (at radial distances of 20–30 R E ) in association with substorm onsets made by Geotail over the period of 1994–2019. Magnetic reconnection can be observed in the 21–02 MLT (corresponding to the region of Y GSM = +15 to −10 R E ).…”

Section: Introductionmentioning

confidence: 99%

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Solar Wind Energy Input: The Primary Control Factor of Magnetotail Reconnection Site

Nagai¹,

Shinohara

2022

JGR Space Physics

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Magnetic reconnection occurs in the near-Earth magnetotail in association with the onset of magnetospheric substorms. It converts magnetic energy that is previously stored in the magnetotail to plasma kinetic and thermal energy and produces various dynamic phenomena in the magnetosphere-ionosphere system. It produces fast plasma flows, which are observed more frequently in the premidnight (dusk) sector of the plasma sheet relative to those in the postmidnight (dawn) sector (e.g., Nagai et al., 1998). Satellite observations reveal that the occurrence of auroral brightening is high in the 21-24 magnetic local time (MLT) range (e.g., Frey et al., 2004;Liou et al., 2001). Hence, the tail fast plasma flow results are consistent with the occurrence of auroral brightening corresponding to an onset of substorms.Nagai and Shinohara (2021) reported distribution of in situ magnetic reconnection observations in the near-Earth magnetotail (at radial distances of 20-30 R E ) in association with substorm onsets made by Geotail over the period of 1994-2019. Magnetic reconnection can be observed in the 21-02 MLT (corresponding to the region of Y GSM = +15 to −10 R E ). The important finding of their study is that magnetic reconnection has a short dawn-dusk X-line corresponding to 1-hr MLT. There are several examples of magnetic reconnection in the postmidnight sector of the plasma sheet, and they are mostly observed in highly active geomagnetic conditions and storms by Geotail (Nagai et al., 2013(Nagai et al., , 2015. The Cluster mission observed the ion diffusion region in magnetic reconnection near Y GSM = −5 R E (Eastwood et al., 2010), and the postmidnight event on 21 August 2002 was observed during a storm. During an intense storm on 28 May 2017, the Magnetospheric Multiscale mission made in situ observations of the ion diffusion region at ( et al., 2019). Hence, magnetic reconnection can be formed in the postmidnight sector of the plasma sheet. It may be conceivable that magnetic reconnection observed in the postmidnight sector is a dawnward extension of the X-line initially formed in the premidnight sector. However, magnetic reconnection in the postmidnight sector produces a substorm current system in the same sector. Any dawnward or duskward extension of the X-line is not confirmed (Nagai & Shinohara, 2021).It is reasonable to attribute an onset of magnetic reconnection to pre-conditions in the plasma sheet during the loading period (the growth phase of substorms). In the growth phase of a substorm, magnetic field lines are transported to the magnetotail as the loading process, and the magnetic field intensity increases in the tail lobes (e.g.,

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Section: Mcpherronmentioning

confidence: 99%

Section: Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Solar Wind Energy Input: The Primary Control Factor of Magnetotail Reconnection Site

Nagai¹,

Shinohara

2022

JGR Space Physics

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“…Then, the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission was proposed to identify the controversy of these models (Angelopoulos, 2008). The current understanding is that both models can work at a substorm onset, although which one is more significant is still unresolved (See Lui, 2015 versus Nagai andShinohara, 2021 for the present state of the controversy). But I could not contribute much to these developments of new missions and subsequent substorm discussion.…”

Section: Connection Between Flow Braking and Substorm Processesmentioning

confidence: 99%

A Story of Developing the Idea of Plasma-Sheet Flow Braking

Shiokawa

2022

Front. Astron. Space Sci.

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This paper reports a story of developing the idea of Earthward ion flow braking in the near-Earth plasma sheet and its relationship with substorm onset processes. This idea and the data that support it are the basis for today’s two competing models for substorms: the near-Earth neutral-line model and the current disruption model. The idea was developed when the author was staying at the Max Planck Institute for Extraterrestrial Physics (MPE) from July 1996 to June 1997. The story addresses the colleagues and mentors who had contributed to the development of this idea. The lessons learned from this story are also summarized for students and early-career scientists for their development of new scientific ideas.

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