Thermodynamics of the Magnetotail Current Sheet Thinning

Yushkov, E. V.; Petrukovich, A. A.; Artemyev, А. V.; Nakamura, R.

doi:10.1029/2020ja028969

Cited by 12 publications

(16 citation statements)

References 67 publications

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“…The main signatures of the current sheet thinning are a decrease of the equatorial magnetic field B z (hereinafter Geocentric Solar Magnetospheric (GSM) coordinates are used), an increase of the equatorial current density j y , and a less‐pronounced increase of the lobe magnetic field B L (see, e.g., Birn et al., 1998; Schindler & Birn, 1982, 1993). These signatures are quite repeatable and well‐documented by a number of authors using past single and more recent multi‐spacecraft missions (Artemyev, Angelopoulos, Runov, & Petrukovich, 2016; Petrukovich et al., 2007; Sergeev et al., 2011; Snekvik et al., 2012; Yushkov et al., 2021). Simulations using magnetohydrodynamical (MHD) analytical models (e.g., Birn et al., 2004), numerical 3D MHD (e.g., Gordeev et al., 2017; Hsieh & Otto, 2015), hybrid (Lu, Artemyev, Angelopoulos, Lin, et al., 2019; Lu et al., 2016) and particle‐in‐cell (e.g., Lu et al., 2018) approaches also reproduce these signatures rather faithfully.…”

Section: Introductionsupporting

confidence: 60%

Thinning of the Magnetotail Current Sheet Inferred From Low‐Altitude Observations of Energetic Electrons

et al. 2022

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scales, resulting in the magnetic field line reconnection (and subsequent reconfiguration, i. e., the so-called dipolarization) that mark the substorm onset (see discussion of various onset scenarios in Sitnov et al., 2013Sitnov et al., , 2017. The reconnection process and the efficiency of magnetic field energy conversion to particle kinetic energy are highly dependent upon the pre-reconnection thin current sheet configuration (see discussion in

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Section: Introductionsupporting

confidence: 60%

Thinning of the Magnetotail Current Sheet Inferred From Low‐Altitude Observations of Energetic Electrons

et al. 2022

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“…It is accompanied by an increase in the total pressure of the plasma sheet, which is mainly caused by an increase in the plasma density (e.g., Nagai et al., 1997). However, it is not simply caused by any pressure balance effect (e.g., Saito et al., 2011; Sergeev et al., 2011; Yushkov et al., 2021), and plasma transport processes should operate (e.g., Hsieh & Otto, 2015). Since it is difficult to sample many plasma flows during the pure growth phase (not affected by previous substorm activities) by spacecraft in the plasma sheet, the plasma flow pattern producing the dynamics during the growth phase is not well explored.…”

Section: Introductionmentioning

confidence: 99%

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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“…Let us discuss ranges of these parameters derived from spacecraft observations in the near-Earth magnetotail. The current sheet thickness L z varies from 500 km to 5000 km for most of observed magnetotail current sheets 9,27 , and L z is larger for post-dipolarization current sheet 53 . The dipolarization front thickness L x is generally smaller than 1000 km (see Refs.…”

Section: Charged Particle Dynamicsmentioning

confidence: 96%

Charged particle scattering in dipolarized magnetotail

Lukin,

Artemyev,

Petrukovich

et al. 2021

Preprint

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The Earth's magnetotail is characterized by stretched magnetic field lines. Energetic particles are effectively scattered due to the field-line curvature, which then leads to isotropization of energetic particle distributions and particle precipitation to the Earth's atmosphere. Measurements of these precipitation at low-altitude spacecraft are thus often used to remotely probe the magnetotail current sheet configuration. This configuration may include spatially localized maxima of the curvature radius at equator (due to localized humps of the equatorial magnetic field magnitude) that reduce the energetic particle scattering and precipitation. Therefore, the measured precipitation patterns are related to the spatial distribution of the equatorial curvature radius that is determined by the magnetotail current sheet configuration. In this study, we show that, contrary to previous thoughts, the magnetic field line configuration with the localized curvature radius maximum can actually enhance the scattering and subsequent precipitation. The spatially localized magnetic field dipolarization (magnetic field humps) can significantly curve magnetic field lines far from the equator and create off-equatorial minima in the curvature radius. Scattering of energetic particles in these off-equatorial regions alters the scattering (and precipitation) patterns, which has not been studied yet. We discuss our results in the context of remote-sensing the magnetotail current sheet configuration with low-altitude spacecraft measurements.

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Thermodynamics of the Magnetotail Current Sheet Thinning

Cited by 12 publications

References 67 publications

Thinning of the Magnetotail Current Sheet Inferred From Low‐Altitude Observations of Energetic Electrons

Thinning of the Magnetotail Current Sheet Inferred From Low‐Altitude Observations of Energetic Electrons

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

Charged particle scattering in dipolarized magnetotail

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