Cluster observations of the dusk flank magnetopause near the sash: Ion dynamics and flow‐through reconnection

Maynard, N. C.; Farrugia, Charles J.; Burke, William J.; Ober, D. M.; Mozer, F. S.; Rème, H.; Dunlop, M. W.; Siebert, K. D.

doi:10.1029/2012ja017703

Cited by 13 publications

(11 citation statements)

References 56 publications

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“…In addition, δ e exhibits a weak enhancement, forming a line starting at ( B L =1.5 nT, B N =−0.5 nT), extending northward and toward the magnetosheath. Along this line, at ( B L =−0.8 nT, B N =−1.2 nT), MMS 2 made a single observation where δ e >1, which indicates that the electrons are fully demagnetized [ Maynard et al , ; Scudder et al , ].…”

Section: Resultsmentioning

confidence: 99%

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EDR signatures observed by MMS in the 16 October event presented in a 2‐D parametric space

et al. 2017

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We present a method for mapping the position of satellites relative to the X line using the measured BL and BN components of the magnetic field and apply it to the Magnetospheric multiscale (MMS) encounter with the electron diffusion region (EDR) which occurred on 13:07 UT on 16 October 2015. Mapping the data to our parametric space succeeds in capturing many of the signatures associated with magnetic reconnection and the electron diffusion region. This offers a method for determining where in the reconnection region the satellites were located. In addition, parametric mapping can also be used to present data from numerical simulations. This facilitates comparing data from simulations with data from in situ observations as one can avoid the complicated process using boundary motion analysis to determine the geometry of the reconnection region. In parametric space we can identify the EDR based on the collocation of several reconnection signatures, such as electron nongyrotropy, electron demagnetization, parallel electric fields, and energy dissipation. The EDR extends 2–3 km in the normal direction and in excess of 20 km in the tangential direction. It is clear that the EDR occurs on the magnetospheric side of the topological X line, which is expected in asymmetric reconnection. Furthermore, we can observe a north‐south asymmetry, where the EDR occurs north of the peak in out‐of‐plane current, which may be due to the small but finite guide field.

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Section: Resultsmentioning

confidence: 99%

“…It is defined as

δ_{e} = \frac{| boldE + {boldv}_{e} \times boldB |}{w_{⊥ e} B},

where v e is the electron bulk velocity, e is elementary charge, and w ⊥ e is the thermal speed of the electrons [ Scudder and Daughton , ; Scudder et al , ]. A particle can be considered to be fully demagnetized if δ e >1 [ Maynard et al , ].…”

Section: Introductionmentioning

confidence: 99%

EDR signatures observed by MMS in the 16 October event presented in a 2‐D parametric space

et al. 2017

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“…It gives a scalar measure of the level of demagnetization of the ions. A value of δ i << 1 implies that the ions are magnetized while a δ i >1 means that they are fully demagnetized (Maynard et al, ; Scudder et al, ). The observations here suggest that in the outbound crossing MMS1 is passing through the IDR.…”

Section: Observationsmentioning

confidence: 99%

MMS Observations of Reconnection at Dayside Magnetopause Crossings During Transitions of the Solar Wind to Sub‐Alfvénic Flow

et al. 2017

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We present MMS observations during two dayside magnetopause crossings under hitherto unexamined conditions: (i) when the bow shock is weakening and the solar wind transitioning to sub‐Alfvénic flow and (ii) when it is reforming. Interplanetary conditions consist of a magnetic cloud with (i) a strong B (∼20 nT) pointing south and (ii) a density profile with episodic decreases to values of ∼0.3 cm−3 followed by moderate recovery. During the crossings the magnetosheath magnetic field is stronger than the magnetosphere field by a factor of ∼2.2. As a result, during the outbound crossing through the ion diffusion region, MMS observed an inversion of the relative positions of the X and stagnation (S) lines from that typically the case: the S line was closer to the magnetosheath side. The S line appears in the form of a slow expansion fan near which most of the energy dissipation is taking place. While in the magnetosphere between the crossings, MMS observed strong field and flow perturbations, which we argue to be due to kinetic Alfvén waves. During the reconnection interval, whistler mode waves generated by an electron temperature anisotropy (Te⊥>Te∥) were observed. Another aim of the paper is to distinguish bow shock‐induced field and flow perturbations from reconnection‐related signatures. The high‐resolution MMS data together with 2‐D hybrid simulations of bow shock dynamics helped us to distinguish between the two sources. We show examples of bow shock‐related effects (such as heating) and reconnection effects such as accelerated flows satisfying the Walén relation.

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“…We now advance plausible evidence of entries into the ion DR during these crossings. One diagnostic for this is given by the adiabatic expansion parameter, δ i [ Scudder et al , ; see also Maynard et al , ]. This quantity is defined as

δ_{i} \equiv \frac{| E_{⟂} + V_{i} \times B |}{w_{⟂ i} B}

where

w_{⟂ i} \equiv \sqrt{2 k T_{⟂ i} / m_{i}}

represents the mean thermal speeds of ions.…”

Section: In Situ Observations: Polarmentioning

confidence: 99%

Structure of a reconnection layer poleward of the cusp: Extreme density asymmetry and a guide field

et al. 2014

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We present Polar observations of a reconnection layer during an inbound pass at high northern latitudes. The interplanetary field of 20 nT pointed strongly northward continuously for 13 h. Reverse polar cap convection observed repeatedly by the DMSP F13 satellite provided direct evidence of continued reconnection. Polar observed sunward and southward jets. The event was hallmarked by a density asymmetry ≈140 and moderate guide field. Disturbances in fields and plasma were much more intense on the magnetosphere (MSP) side of the current sheet (CS). A density cavity was observed at both separatrices. Isolated EN peaks occurred at the density cavity regions. The intense electric field fluctuations (≤60 mV/m) were mainly in the component normal to the CS, EN. The guide field pointed opposite to the Hall field, leading to an overall weakening of the out‐of‐plane magnetic field. A magnetic island was observed in the outflow jet. The field reversal at the CS occurred before the outflow jet, which we argue to be due to the large density asymmetry. The stagnation line was strongly shifted toward the MSP side of the CS. We compare observations with simulations which emphasize the density asymmetry and which also include a guide field, and we find good agreement. Remaining discrepancies may be explained by a density asymmetry much larger than in simulations. This is to our knowledge the first study of a high‐latitude reconnection layer with (1) an extreme density asymmetry and (2) steady and continuously strong interplanetary Bz.

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Cluster observations of the dusk flank magnetopause near the sash: Ion dynamics and flow‐through reconnection

Cited by 13 publications

References 56 publications

EDR signatures observed by MMS in the 16 October event presented in a 2‐D parametric space

EDR signatures observed by MMS in the 16 October event presented in a 2‐D parametric space

MMS Observations of Reconnection at Dayside Magnetopause Crossings During Transitions of the Solar Wind to Sub‐Alfvénic Flow

Structure of a reconnection layer poleward of the cusp: Extreme density asymmetry and a guide field

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