Determining L - M - N Current Sheet Coordinates at the Magnetopause From Magnetospheric Multiscale Data

The microphysics in the separatrix region (SR) plays an important role for the energy conversion in reconnection. Based on the Magnetospheric Multiscale observations in the magnetotail, we present a complete crossing of the current sheet with ongoing magnetic reconnection. The field&#8208;aligned inflowing electrons were observed in both separatrix regions (SRs) and their energy extended up to several times of the thermal energy. Along the SR, a net parallel electrostatic potential was estimated and could be the reason for the inflowing electron streaming. In the northern SR, the electron frozen&#8208;in condition was violated and nonideal electric field was inferred to be caused by the gradient of the electron pressure tensor. The nongyrotropic electron distribution and significant energy dissipation were observed at the same region. The observations indicate that the inner electron diffusion region can extend along the separatrices or some electron&#8208;scale instability can be destabilized in the SR.&#160;

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MMS Observations of Short-Period Current Sheet Flapping

10.5194/egusphere-egu2020-8693 ◽

2020 ◽

Author(s):

Louis Richard ◽

Yuri Khotyaintsev ◽

Daniel Graham ◽

Christopher Russell ◽

Olivier Le Contel

Keyword(s):

Current Sheet ◽

Ecliptic Plane ◽

Minimum Variance ◽

Current Sheets ◽

Magnetospheric Multiscale ◽

Short Period ◽

Wave Modes

Flapping motions of current sheets are commonly observed in the magnetotail. Various wave modes can correspond to these oscillations such as kink-like flapping or steady flapping (e.g Wei2019). The period of such oscillating phenomena is usually longer than 100s and a typical observations consist only of a few crossings (e.g. Zhang2002). Here, we present a short period (T&#8776;25s) flapping event observed by Magnetospheric Multiscale (MMS) mission at the dusk side plasmasheet on September 14, 2019. Using the multispacecraft observations, the direction of flapping as well as the direction of propagation of the current sheet are determined using the minimum variance, the timing method and the spatiotemporal derivative (Shi2005). It appears that the three methods give similar results with a direction of propagation of the current sheet which mainly lies in the ecliptic plane with a flapping velocity up to 500km/s. Based on the obtained wavelength and the variations of the direction of propagation we discuss which of the wave modes can explain the flapping.

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Electron-only Reconnection in an Ion-scale Current Sheet at the Magnetopause

The Astrophysical Journal ◽

10.3847/1538-4357/ac2668 ◽

2021 ◽

Vol 922 (1) ◽

pp. 54

Author(s):

S. Y. Huang ◽

Q. Y. Xiong ◽

L. F. Song ◽

J. Nan ◽

Z. G. Yuan ◽

...

Keyword(s):

Magnetic Field ◽

Standard Model ◽

Magnetic Reconnection ◽

Current Sheet ◽

Diffusion Region ◽

Ion Outflow ◽

Magnetospheric Multiscale ◽

The Standard Model ◽

Field Lines ◽

Reconnection Model

Abstract In the standard model of magnetic reconnection, both ions and electrons couple to the newly reconnected magnetic field lines and are ejected away from the reconnection diffusion region in the form of bidirectional burst ion/electron jets. Recent observations propose a new model: electron-only magnetic reconnection without ion coupling in an electron-scale current sheet. Based on the data from the Magnetospheric Multiscale (MMS) mission, we observe a long-extension inner electron diffusion region (EDR) at least 40 d i away from the X-line at the Earth’s magnetopause, implying that the extension of EDR is much longer than the prediction of the theory and simulations. This inner EDR is embedded in an ion-scale current sheet (the width of ∼4 d i, d i is ion inertial length). However, such ongoing magnetic reconnection was not accompanied with burst ion outflow, implying the presence of electron-only reconnection in an ion-scale current sheet. Our observations present a new challenge for understanding the model of standard magnetic reconnection and the electron-only reconnection model in an electron-scale current sheet.

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MMS Observations of FTE-Type Structures with Internal Magnetic Reconnection

10.5194/egusphere-egu2020-15878 ◽

2020 ◽

Author(s):

Rungployphan Kieokaew ◽

Benoit Lavraud ◽

Naïs Fargette

Keyword(s):

Magnetic Flux ◽

Magnetic Reconnection ◽

Current Sheet ◽

Flux Rope ◽

Formation Mechanisms ◽

Transfer Event ◽

Flux Tubes ◽

Magnetospheric Multiscale ◽

Spacecraft Data ◽

Upstream Solar Wind

A bipolar magnetic variation Bn with enhanced core and total fields in spacecraft data are recognized as a Flux Transfer Event (FTE) signature, which corresponds to the passage of a magnetic flux rope structure. Recent literature reported Magnetospheric Multiscale (MMS) observations of FTE signatures with magnetic reconnection signatures at the central current sheet. Among reported cases, electron pitch angle distributions (ePAD) in the suprathermal energy range show different features on either side of the reconnecting current sheet, indicating different magnetic connectivities. This structure is interpreted as interlinked/interlaced flux tubes, possibly formed by converging jets toward the central current sheet that in turn enhance magnetic flux pile-up and facilitate reconnection at the current sheet separating the two flux tubes. By surveying similar events using MMS data, we found some FTE-type structures with reconnection signatures at the central current sheet but with homogeneous ePAD of suprathermal electrons across the structures. Thus, these structures are inconsistent with interlinked flux tubes, but rather a regular flux rope. This leads to a question of how reconnection can occur in those single flux ropes, and their relation with interlinked flux tubes. In this work, we investigate properties of these structures and their related upstream solar-wind conditions. Formation mechanisms of such structures and how reconnection can occur will be discussed.

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MMS-Cluster conjugate observation of disturbance in the current sheet associated with localized fast flow in the near-Earth magnetotail

10.5194/egusphere-egu2020-3254 ◽

2020 ◽

Author(s):

Rumi Nakamura ◽

Wolfgang Baumjohann ◽

Joachim Birn ◽

Jim Burch ◽

Chris Carr ◽

...

Keyword(s):

Current Sheet ◽

Equatorial Region ◽

Small Scale ◽

Dipolarization Front ◽

Magnetospheric Multiscale ◽

Statistical Studies ◽

Point Data ◽

Fast Flow ◽

Magnetotail Dynamics

We report the evolution of the current sheet associated with a localized flow burst in the near-Earth magnetotail on Sep. 8, 2018 around 14 UT when MMS (Magnetospheric Multiscale) and Cluster at about X=17 RE, separated mainly in the dawn-dusk direction at a distance of about 4 RE, encountered at duskside and dawnside part of a dipolarization front, respectively.&#160; We analyzed the mesoscale current sheet disturbances based on multi-point data analysis between Cluster and MMS. It is shown that the current sheet thickens associated with the passage of the dipolarization front confirming results from previous statistical studies. The thickness of the current sheet, however, decreased subsequently, before recovering toward the original configuration. MMS observed enhanced field aligned currents exclusively during this thinning of the current sheet at the off-equatorial region. Multiple layers of small-scale, intense field-aligned currents accompanied by enhanced Hall-currents were detected at this region.&#160; Based on these mesoscale and microscale multipoint observations, we infer the current structures around the localized flow and discuss the role of these mesoscale flow processes in the larger-scale magnetotail dynamics.&#160;&#160;

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