Displays

For reconnection at the Earth’s day side, which is asymmetric, the main energy conversion occurs on closed field lines in the electron stagnation region. Energy conversion, as measured by J⦁E, occurs where out-of-plane electric field components are embedded within larger regions of out-of-plane current, which is carried by strong electron flows in the M direction of the LMN coordinate system. Bracketing these energy conversion sites are electron jet reversals (along L and -L) and converging  electron flows (along N and -N). These electron flows are like those that surround reconnection X lines, however, in these cases they occur completely within closed field lines. The question then is what, if anything, this energy conversion has to do with local reconnection of magnetic field lines. This paper reports on a study of two events observed by MMS on December 29, 2016 and April 15, 2018. The electron inflows have velocities between 0.05 V_eA and 0.1 V_eA, (V_eA = electron Alfvén speed), which are consistent with predicted reconnection rates. Laboratory measurements and 3D simulation results offer some clues about how reconnecting current sheets can evolve in a uniform background magnetic field.

How to cite: Burch, J., Webster, J., Pritchard, K., Genestreti, K., Hesse, M., Cassak, P., Torbert, R., Giles, B., Ergun, R., Russell, C., Strangeway, R., Hwang, K.-J., Dokgo, K., and Fuselier, S.: Energy Conversion in the Electron Stagnation Region of Magnetopause Reconnection, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3757, https://doi.org/10.5194/egusphere-egu2020-3757, 2020.

One of the most important transient phenomena affecting the solar wind-Earth’s magnetosphere coupling is non-steady dayside magnetic reconnection, observationally evidenced by a transient structure consisting of a bipolar magnetic-field component normal to the magnetopause. This signature, termed a flux-transfer-event (FTE), has been recently found to often consist of two interlinked flux tubes. The recent observations, particularly from the MMS spacecraft, showed a reconnecting current sheet between the interlaced flux tubes. However, local kinetic processes between the flux tubes have not been understood in the context of the broader FTE structure and evolution. An FTE observed by MMS on 18 December, 2017 comprised two flux tubes of different topology. One includes field lines with their ends connected to the northern and southern hemispheres while the other includes field lines that are connected to the magnetosheath (and ultimately the Sun). Evidence for reconnection occurring at the interface of the two flux tubes indicates how interacting flux tubes evolve into a flux rope having helical magnetic topology connecting either both to the Earth or being completely open. This study proposes a new aspect of how micro-to-meso-scale dynamics occurring within FTEs determines the macroscale characteristics and evolution of the structures.

How to cite: Hwang, K., Burch, J., Russell, C., Choi, E., Dokgo, K., Fear, R., Fuselier, S., Petrinec, S., Sibeck, D., Hasegawa, H., Fu, H., Øieroset, M., Escoubet, P., Giles, B., Strangeway, R., Khotyaintsev, Y., Graham, D., Gershman, D., Pollock, C., and Ergun, R. and the MMS science working group: Local kinetic processes determining macroscopic properties of interlinked magnetic flux tubes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3699, https://doi.org/10.5194/egusphere-egu2020-3699, 2020.

Flux transfer events are transient magnetized plasma structures that are self-balancing, rope-like phenomena that appear when the interplanetary magnetic field is southward. Using measurements of particles and magnetic fields on the MMS spacecraft, we find that these structures contain magnetospheric energetic electrons in exactly half of their observations, independent of external conditions or locations. This implies that two flux ropes are created for each event, one connected to the magnetosphere and one not connected. We show that this dual nature occurs independent of solar wind properties and location of observation. These observations are consistent with a recent model of flux transfer event generation.

How to cite: Russell, C. and Strangeway, R.: Flux Transfer Events are Made in Pairs, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2239, https://doi.org/10.5194/egusphere-egu2020-2239, 2020.

When the magnetic field is oriented nearly perpendicular to the direction of the plasma shear flow, the flow easily satisfies the super-Alfvénic unstable condition for the Kelvin-Helmholtz (KH) instability. This configuration is realized at the Earth’s low-latitude magnetopause when the interplanetary magnetic field (IMF) is strongly northward or southward. Indeed, clear signatures of the KH waves have been frequently observed during periods of the northward IMF. However, these signatures have been much less frequently observed during the southward IMF. In this work, we performed the first 3-D fully kinetic simulation of the KH instability at the magnetopause under the southward IMF condition. The simulation demonstrates that magnetic reconnection, with a typical fast rate on the order of 0.1, is induced at multiple locations along the vortex edge in an early non-linear growth phase of the KH instability. The reconnection outflow jet, which grows in the direction nearly perpendicular to the initial shear flow, significantly disrupt the flow of the non-linear KH vortex. On the other hand, the shear and vortex flow strongly bends and twists the reconnected field lines towards the direction out of the reconnection plane. The resulting coupling of the complex field and flow patterns within the magnetopause boundary layer leads to a quick decay of the vortex structure. These simulation results suggest that clear signatures of the KH waves are expected to be observed only for a limited phase during periods of the southward IMF, which may explain the difference in the observation probability of KH waves between northward and southward IMFs.

How to cite: Nakamura, T., Plaschke, F., Hasegawa, H., Liu, Y.-H., Hwang, K.-J., Blasl, K. A., and Nakamura, R.: Magnetic reconnection induced by the Kelvin-Helmholtz vortex at the Earth’s magnetopause during southward IMF, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4027, https://doi.org/10.5194/egusphere-egu2020-4027, 2020.

Magnetic reconnection is a fundamental plasma physics process which governs energy and mass transfer from the solar wind into the Earth’s magnetosphere. Electron acceleration during reconnection has been widely investigated with multiple mechanisms proposed. Many of these mechanisms involve flux ropes: twisted magnetic field structures formed during reconnection. Drake et al. 2006 suggest that contracting magnetic islands (or flux ropes in 3D) could trap and energise electrons by a Fermi acceleration process.

Whilst previous missions have observed and characterised flux ropes, the temporal resolution of the data was typically not great enough to study structures in detail, particularly on electron scales. Here we investigate magnetopause flux ropes using data from NASA’s four spacecraft Magnetospheric Multiscale mission (MMS). MMS measures the thermal electron and ion 3D distribution at 30 msec and 150 msec time resolution, respectively, and at spacecraft separations down to a few kilometers.

We focus on electron pitch angle distributions and examine how they can be used to investigate magnetopause flux ropes. In particular, the distributions are used to identify electron trapping in magnetic mirror structures on the magnetospheric edge of the flux ropes. These features are found to have extended 3D structure along the body of the flux rope. We evaluate possible formation mechanisms, such as the mirror instability, and potential electron acceleration mechanisms, such as betatron and Fermi acceleration. Magnetic mirror structures could represent an important particle acceleration feature for flux ropes and magnetic reconnection.

How to cite: Robertson, S., Eastwood, J., Stawarz, J., Hietala, H., Phan, T., Lavraud, B., Burch, J., Giles, B., Gershman, D., Torbert, R., Lindqvist, P. A., Ergun, R., Russell, C., and Strangeway, R.: Magnetic mirror structures associated with magnetopause flux ropes investigated with Mangnetospheric Multiscale misson (MMS), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11373, https://doi.org/10.5194/egusphere-egu2020-11373, 2020.

The interplanetary magnetic field (IMF) convected with the solar wind drapes around the region of space dominated by Earth’s geomagnetic field and undergoes a process called magnetic reconnection at the magnetopause; the boundary layer that separates these two distinct regimes. Magnetic reconnection changes the topology of magnetic field lines and is known to convert magnetic energy into kinetic energy and heat. This fundamental process occurs in many environments, spanning from laboratory plasmas to the heliosphere, the solar atmosphere, and to astrophysical phenomena. Magnetic reconnection at the Earth’s magnetopause has been observed at various times and places as either anti-parallel and/or component reconnection. A model known as the Maximum Magnetic Shear Model combines these two scenarios, creating long reconnection lines crossing the dayside magnetopause along a ridge of maximum magnetic shear. 
The connection points between the anti-parallel and the component reconnection segments of the reconnection line are known as ‘Knee’ regions. Using observations from the MMS satellites, it was shown that the location of the Knee region depends strongly on the local draping conditions of the IMF across the magnetopause, with certain draping conditions causing a deflection of the location along the anti-parallel reconnection region. This study discusses an event that shows that the entire component reconnection X-line crossing the dayside magnetopause can be affected by this deflection. This result emphasizes the importance of anti-parallel reconnection that seems to control where component reconnection is occurring. 

How to cite: Trattner, K., Fuselier, S., Petrinec, S., Burch, J., Cassak, P., Ergun, R., Giles, B., and Torbert, R.: The location of Component Reconnection at the Earth’s Magnetopause During Dominant IMF By and Large Dipole Tilt Conditions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3156, https://doi.org/10.5194/egusphere-egu2020-3156, 2020.

Our group has done extensive research on the fluid and kinetic effect of cold ion populations on the reconnection process, in an effort to identify factors that can lead to the onset or stopping of magnetic reconnection. Recent fully kinetic studies involving cold protons or oxygen have shown that flows of cold particles significantly modify the reconnection process, and that the nature of this modification is dependent on the configuration of these flows and the constituent ions of the flows. In this study we want to investigate how the reconnection process is affected by a shear flow of cold protons outside of the current sheet, using a 2.5D Particle-In-Cell simulation. The effect of shear flows on magnetic reconnection has investigated earlier, indicating a signifficant modification of the reconnection process. However, it is not clear how these effects will be influenced by the additional scale lengths introduced into the system by a cold ion flow. In particular we want to investigate how the current sheet and diffusion regions are altered by a cold shear flow on a kinetic level, and how the reconnection process is altered on ion scales and beyond. Preliminary results indicate that the shear flow introduces a tilt of the current sheet, which appears to be consistent with earlier studies. Results will be compared to our group’s earlier results involving symmetric and asymmetric flows of cold particles in the inflow regions, as well as existing simulations and observations of magnetic reconnection including warm shear flows.

How to cite: Flø Spinnangr, S., Tenfjord, P., Hesse, M., Norgren, C., and Kwagala, N.: Particle-In-Cell simulations of magnetic reconnection in the presence of a cold shear flow, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16473, https://doi.org/10.5194/egusphere-egu2020-16473, 2020.

The Earth’s magnetosheath is filled with small-scale current sheets arising from turbulent dynamics in the plasma. Previous observations and simulations have provided evidence that such current sheets can be sites for magnetic reconnection. Recently, observations from the Magnetospheric Multiscale (MMS) mission have revealed that a novel form of “electron-only” reconnection can occur at these small-scale, turbulence-driven current sheets, in which ions do not appear to couple to the reconnected magnetic field to form ion jets. The presence of electron-only reconnection may facilitate dissipation of the turbulence, thereby influencing the partition of energy between ions and electrons, and can alter the nonlinear dynamics of the turbulence itself. In this study, we perform a survey of turbulent intervals in the Earth’s magnetosheath as observed by MMS in order to determine how common magnetic reconnection is in the turbulent magnetosheath and how it impacts the small-scale turbulent dynamics. The magnetic correlation length, which dictates the length of the turbulent current sheets, is short enough in most of the examined intervals for reconnection with reduced or absent ion jets to occur. Magnetic reconnection is found to be a common feature within these intervals, with a significant fraction of reconnecting current sheets showing evidence of sub-Alfvénic ion jets and super- Alfvénic electron jets, consistent with electron-only reconnection. Moreover, a subset of the intervals exhibit changes in the behavior of the small-scale magnetic power spectra, which may be related to the reconnecting current sheets. The results of the survey are compared with recent theoretical work on electron-only reconnection in turbulent plasmas.

How to cite: Stawarz, J. E., Eastwood, J. P., Phan, T., Gingell, I. L., Mallet, A., Shay, M. A., Sharma Pyakurel, P., Burch, J. L., Ergun, R. E., Giles, B. L., Gershman, D. J., Le Contel, O., Lindqvist, P.-A., Strangeway, R. J., Torbert, R. B., Argall, M. R., Fischer, D., and Magnes, W.: The Relationship Between Electron-Only Magnetic Reconnection and Turbulence in Earth’s Magnetosheath, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5692, https://doi.org/10.5194/egusphere-egu2020-5692, 2020.

Satellite observations with high-resolution measurements have demonstrated the existence of intermittent current sheets and occurrence of magnetic reconnection in a quasi-parallel magnetosheath behind the terrestrial bow shock. In this Letter, by performing a three-dimensional (3-D) global hybrid simulation, we investigated the characteristics of the quasi-parallel magnetosheath of the bow shock, which is formed due to the interaction of the solar wind with the earth’s magnetosphere. Current sheets with widths of several ion inertial lengths are found to be produced in the magnetosheath after the upstream large amplitude electromagnetic waves penetrate through the shock and are then compressed in the downstream. Magnetic reconnection consequently occurs in these current sheets, where high-speed ion flow jets are identified in the outflow region. Simultaneously, flux ropes with the extension (along the   direction) of about several earth’s radii are also observed. Our simulation shed new insight on the mechanism for the occurrence of magnetic reconnection in the quasi-parallel shocked magnetosheath.

How to cite: Lu, Q., Wang, H., and Wang, X.: Turbulence-driven magnetic reconnection in the magnetosheath downstream of a quasi-parallel shock：a three-dimensional global hybrid simulation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21406, https://doi.org/10.5194/egusphere-egu2020-21406, 2020.

Dipolarization front—a sharp boundary leading reconnection jets and producing colorful auroras—plays a crucial role in the magnetotail energy conversion. Behind this front, sometimes energetic electrons appear, whereas sometimes they vanish. The reason causing such uncertainty is still a mystery, owing to the lack of high-resolution measurements. Here we propose a novel model to uncover this mystery: we find that behind the front there exists a magnetic bottle with time-varying belly but steady neck. When the belly is expanding—like a man getting fat—the magnetic bottle is formed and energetic electrons are trapped; when the belly is contracting—like a man getting slim—the magnetic bottle disappears and energetic electrons are expelled. This model clearly explains how energetic electrons are trapped in the Earth’s magnetotail and in principle it can be applied to other planetary magnetotails. 

How to cite: Fu, H., Zhao, M., Yu, Y., and Wang, Z.: A new model to explain energetic electrons behind dipolarization front, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1866, https://doi.org/10.5194/egusphere-egu2020-1866, 2020.

We investigate magnetic compression near the reconnection separatrix observed by Magnetospheric MultiScale (MMS) on July 11^th 2017. A clear transition between inflow and outflow in both ions and electrons is observed across an ion gyro-scale region of enhanced magnetic field. Multispacecraft techniques for magnetic curvature and local gradients along with timing of highly-correlated wave packets are used to determine the spatial configuration of the compressed region. Structure of the system is found to be inherently three dimensional; electron beam-driven modes propagating parallel to the magnetic field are observed concurrent with perpendicular-propagating lower hybrid waves. Larger scale surface waves are also present behind the compression front. Transforming to a deHoffmann-Teller frame across the boundary results in a distinctly non-rotational discontinuity with structure similar to a quasi-2D, Petschek-like slow shock. However, MHD jump conditions are not satisfied, indicating kinetic dissipation may occur within the thin layer. The largest amplitude measurements of $\mathbf{J}\cdot\mathbf{E}$ energy conversion are associated with an inflowing electron beam and parallel electric fields near the magnetic peak. Spikes in $\mathbf{J}\cdot\mathbf{E}$ are predominantly negative, suggesting electron-scale mixing between the reconnection inflow and outflow is partially responsible for the observed magnetic compression.

How to cite: Holmes, J., Nakamura, R., Roberts, O., Schmid, D., Nakamura, T., and Vörös, Z.: Energy conversion by electron beam-driven waves in a compressed reconnection separatrix, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8550, https://doi.org/10.5194/egusphere-egu2020-8550, 2020.

How to cite: Tang, B., Li, W., Graham, D., Wang, C., and Khotyaintsev, Y. and the MMS team: Lower hybrid waves at the magnetosheath separatrix region, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1809, https://doi.org/10.5194/egusphere-egu2020-1809, 2020.

The recently launched NASA’s Magnetosphere Multiscale (MMS) mission enables investigations of multi-scale phenomena in the reconnection process. Especially, the MMS spacecraft revealed that high-frequency waves of electron time scales exist near the electron diffusion region (EDR) due to complex electron distributions. As such waves are generated near the EDR, they could significantly affect the environment of the EDR via wave-particle interactions.

 We investigated the September 19, 2015 event when the MMS spacecraft crossed the reconnection exhaust region. The MMS spacecraft observed a parallel electron crescent, which is known to be generated by the cyclotron turning due to the normal magnetic field in the reconnection exhaust region. At the same time, highly discrete waves were observed in the power spectrum of the electric field. The wave frequency ranged between 6  ~ 14 Fce (Fce: electron cyclotron frequency), and the power of perpendicular components was larger than the parallel component. Therefore, they featured electron Bernstein waves. By modeling the parallel electron crescent as a sum of 18 ring-shaped electron distributions, we calculate the linear dispersion relation using a numerical solver. The linear growth rates agreed with the power spectrum of the electric field, which means that the parallel electron crescent locally drove the electron Bernstein waves. Together with previous studies of high-frequency waves, our work could provide a diagram of high-frequency wave distributions in the reconnection geometry.

How to cite: Dokgo, K., Hwang, K.-J., Burch, J. L., Yoon, P. H., Graham, D. B., and Li, W.: Electron Bernstein waves Driven by the Parallel Electron Crescent in the Reconnection Exhaust Region, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3728, https://doi.org/10.5194/egusphere-egu2020-3728, 2020.

The Earth’s plasmasphere contains cold (~eV energy) dense (>100 cm^-3) plasma of ionospheric origin. The primary ion constituents of the plasmasphere are H⁺ and He⁺, and a lower concentration of O⁺. The outer part of the plasmasphere, especially on the duskside of the Earth, drains away into the dayside outer magnetosphere when geomagnetic activity increases. Because of its high density and low temperature, this plasma has the potential to modify magnetic reconnection at the magnetopause. To investigate the effect of plasmaspheric material at the magnetopause, Magnetospheric Multiscale (MMS) data are surveyed to identify magnetopause crossings with the highest He⁺densities. Plasma wave, ion, and ion composition data are used to determine densities and mass densities of this plasmaspheric material and the magnetosheath plasma adjacent to the magnetopause. These measurements are combined with magnetic field measurements to determine how the highest density plasmaspheric material in the MMS era may affect reconnection at the magnetopause.

How to cite: Fuselier, S., Haaland, S., Tenfjord, P., Malaspina, D., Burch, J., Denton, M., Giles, B., Trattner, K., Petrinec, S., Strangeway, R., and Toledo-Redondo, S.: The effect of plasmaspheric material on magnetopause reconnection, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9760, https://doi.org/10.5194/egusphere-egu2020-9760, 2020.

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‐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‐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‐scale instability can be destabilized in the SR. 

How to cite: Yu, X., Wang, R., and Lu, Q.: Nonideal Electric Field Observed in the Separatrix Region of a Magnetotail Reconnection Event, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2507, https://doi.org/10.5194/egusphere-egu2020-2507, 2020.

By measurements of the Magnetospheric Multiscale (MMS) mission in the magnetotail from -24 to -15 R_E , we identified 40 ion Bursty Bulk Flow events (BBFs) and investigated the electron behaviors during these BBFs. The ion flows peaked near the center of the plasma sheet and had a sharp flow boundary. The electron flow profile is distinct from the ion flows of the BBFs. Inside the BBFs, the strongest earthward electron flows are observed in the ion flow boundary, away from the current sheet center. Further away from the peak of the earthward electron flows, the tailward electron flows are observed in the edges of the ion flows, are mainly field-aligned with low energy, and are stronger than the earthward flows. It seems that the tailward low-energy electrons are energized at some places tailward of the spacecraft and then ejected towards Earth, consistent with the magnetic reconnection scenario in the magnetotail. The implication to the understanding of the astrophysical jets is suggested.

How to cite: Zhang, M. and Lu, Q.: Observation of the tailward electron flows commonly detected at the flow boundary of the earthward ion Bursty Bulk Flows in the magnetotail, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1672, https://doi.org/10.5194/egusphere-egu2020-1672, 2020.

Magnetic field quantization is an important issue for degenerate environments such as neutron star, radio pulsars and magnetars etc., due to the fact that these stars have magnetic field even more than the quantum critical field strength of the order of 4.4×10¹³G, accordingly the cyclotron energy may be equal or even much more than the Fermi energy of degenerate particles. We shall formulate here the exotic physics of strongly magnetized neutron star. The effect of quantized anisotropic magnetic pressure, arising due to a strong magnetic field is studied on the growth rate of Jeans instability of quantum electron–ion and classical dusty plasma.  Here we shall formulate the dispersion equations to govern the propagation of the gravitational waves both in perpendicular and parallel directions to the magnetic field, respectively.  We will depict here that the quantized magnetic field will result in Jeans anisotropic instability such that for perpendicular propagation, the quantized magnetic pressure will stabilize Jeans instability, whereas for the parallel propagation the plasma become more unstable.  We also intend to calculate the corresponding Jeans wave number in the absence of tunneling. The Madelung term leads to the inhomogeneity of the plasma medium. Numerical results are presented to show the effect of the anisotropic magnetic pressure on the Jeans instability.

How to cite: Rozina, C., LevanNodar, T., and Tsintsadze, N.: The magnetic field quantization in pulsar, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22152, https://doi.org/10.5194/egusphere-egu2020-22152, 2020.

Magnetic reconnection in astronomical objects such as solar corona and the Earth’s magnetotail theoretically produces a fast jet toward the object (known as a confined jet as it connects to the object through magnetic field lines) and a fast jet departing the object (known as an unconfined jet as it propagates freely in space). So far, energetic electron acceleration has been observed in the confined jet but never in the unconfined jet, arousing a controversy about whether or not reconnection jets can intrinsically accelerate electrons. Our study is focused on the electron acceleration in unconfined reconnection jet based on Cluster observations and VPIC simulations.

How to cite: Chen, G., Fu, H., Zhang, Y., Li, X., Ge, Y., Du, A., Liu, C., and Xu, Y.: Energetic Electron Acceleration in Unconfined Reconnection Jets, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21853, https://doi.org/10.5194/egusphere-egu2020-21853, 2020.

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.  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.  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.

How to cite: Nakamura, R., Baumjohann, W., Birn, J., Burch, J., Carr, C., Dandouras, I., Escoubet, P., Fazakerley, A., Giles, B., Kubyshkina, M., Le Contel, O., Nagai, T., Nakamura, T., Panov, E., Russell, C., Sergeev, V., and Torbert, R.: MMS-Cluster conjugate observation of disturbance in the current sheet associated with localized fast flow in the near-Earth magnetotail, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3254, https://doi.org/10.5194/egusphere-egu2020-3254, 2020.

Contrary to all the 2D models, where the reconnection x-line extent is infinitely long, we study magnetic reconnection in the opposite limit. The scaling of the average reconnection rate and outflow speed are modeled as a function of the x-line extent. An internal x-line asymmetry along the current direction develops because of the flux transport by electrons beneath the ion kinetic scale, and it plays an important role in suppressing reconnection in the short x-line limit; the average reconnection rate drops because of the limited active region, and the outflow speed reduction is associated with the reduction of the J×B force, that is caused by the phase shift between the J and B profiles, also as a consequence of this flux transport.

How to cite: Huang, K., Liu, Y.-H., Lu, Q., and Hesse, M.: Scaling of magnetic reconnection with a limited x-line extent, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3523, https://doi.org/10.5194/egusphere-egu2020-3523, 2020.

With the observations of THEMIS and MMS Mission, we have investigated the properties of ions in bursty bulk flows (BBFs). Based on analysis of 315 BBF events, we can obtain the statistical features of ions in the BBFs. The results can be summarized as follows: (1) the occurrence rate of BBFs is related with AE index, which is also confirmed by previous studies; (2) the ion number density in the duskside is nearly at the same level with that in the dawnside; (3) in the region -10R_E > X_GSM> -15R_E(where R_Eis the earth radius), the ion temperature in the duskside is much higher than that in the dawnside; (4) the ion temperature anisotropy T_⊥/T_∥ is weaker as BBFs close to the Earth; (5) corresponds to cold electrons (T_e < 1.5 keV), the ratio of the ion and electron temperature T_i/T_e can reach 10-15 and the temperature of ions and electrons have a linear correlation.

How to cite: Wu, M., Pan, Z., Chen, Y., and Zhang, T.: Statistical properties of ions in bursty bulk flows, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4002, https://doi.org/10.5194/egusphere-egu2020-4002, 2020.

The region surrounding the reconnection separatrix consists of the multitude of particle and wave transient features (electron, cold and hot ion beams, Hall E&B fields, kinetic Alfven and LH waves, e-holes etc) whose pattern and intensities may vary depending on the stage of reconnection process as well as on the distance from the active neutral line (XNL), whose characterization from observations is not a trivial task. We explore quick MMS entries into the plasma sheet boundary layer from the lobe in 2017 and 2018 tail seasons which potentially could be the crossings of the active separatrix as suggested by energy dispersed beams and polar rain gap features. By combining  the observations of beam dispersion with the measured plasma convection and PSBL motion (obtained using the timing method) we attempt to separate  temporal and spatial (velocity filter) contributions  to the observed beam energy dispersion and evaluate the MMS distance from the XNL. In this report we discuss similarities and differences of separatrix manifestations  observed far from the XNL (at distances exceeding several tens Re) and those found close to it (where the outermost electron beam directed toward the XNL is seen).  One of surprizes was that we were often able to identify the intense Hall-like E&B field structures at very large distances from the XNL.  

How to cite: Sergeev, V., Apatenkov, S., Nakamura, R., Wellenzohn, S., Plaschke, F., Baumjohann, W., Khotyaintsev, Y., Burch, J., Torbert, R., Russell, C., and Giles, B.: MMS observations of reconnection separatrix region in the magnetotail at different distances from the active neutral X-line , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4615, https://doi.org/10.5194/egusphere-egu2020-4615, 2020.

Interacting with a supersonic solar wind, the escaping ions result in a series of phenomena in the Martian space environment. Observations from MAVEN magnetometer and plasma detector revealed a serial of small-amplitude quasi-monochromatic waves upstream of the Martian bow shock. Those waves have a dominant frequency at the local proton gyrofrequency. The waves evolve into periodic shock structures as they are convected downstream by the high-speed solar wind flow. We found those structures deflected and decelerated solar wind ions through magnetic mirror topology. A consequence of the effect is a significant loss of solar wind ion energy, accompanying with pitch angle scattering.

How to cite: Du, A. and Shan, L.: Deceleration and deflection of solar wind ions by periodic shocks, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6493, https://doi.org/10.5194/egusphere-egu2020-6493, 2020.

The problem of steady symmetrical two-dimensional magnetic reconnection is addressed in terms of the EMHD approximation. In the immediate vicinity of the X-point, this approach has been proven to be an appropriate frame for the reconstruction problem, expressed, particularly, by the Poisson equation for the magnetic potential A, where the right-hand side contains the out-of-plane electron current density with reversed sign. With boundary conditions fixed at some curve (the satellite trajectory), and assuming the right-hand side to be a function of A, one arrives at an ill-posed problem for the Grad-Shafranov equation. The further simplification of the problem may be achieved by using the boundary layer approximation, since magnetic configuration in reconnection region is highly stretched. The benchmark reconstruction of PIC-simulation data, using four numerical techniques, has shown that the main contribution for inaccuracy arises from replacing the Poisson equation by the Grad-Shafranov one. A boundary layer approximation, in turn, does not affect the accuracy significantly; in some cases this approach can appear even the most appropriate. 

How to cite: Korovinskiy, D., Divin, A., Semenov, V., Erkaev, N., and Kiehas, S.: Grad-Shafranov reconstruction of the in-plane magnetic field potential in the X-point vicinity: boundary-layer approximation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8673, https://doi.org/10.5194/egusphere-egu2020-8673, 2020.

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≈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.

How to cite: Richard, L., Khotyaintsev, Y., Graham, D., Russell, C., and Le Contel, O.: MMS Observations of Short-Period Current Sheet Flapping, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8693, https://doi.org/10.5194/egusphere-egu2020-8693, 2020.

It is still unresolved that how magnetic reconnection is triggered in the collisionless environment. In this talk, we will present that the reconnection onset consists of two phases: the electron phase and ion phase. In the electron phase, the electrons are significantly energized and super-alfvenic electron jets are created while the ion bulk flows haven't been formed and the ions haven't been heated. Later on, the ion jets are produced together with the electron jets in the ion phase. The main reason for such two phases is discussed. A particle-in-cell simulation was performed to realize these two phases during reconnection onset. 

How to cite: Wang, R.: magnetic reconnection onset from electron phase to ion phase, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4023, https://doi.org/10.5194/egusphere-egu2020-4023, 2020.

Magnetic reconnection is a universal physical process during which energy can be transferred from the electromagnetic field to the plasma. Energy dissipation in the diffusion region has always been a significant issue for understanding this energy transport. Using the four MMS spacecraft data, we investigate a magnetic reconnection diffusion region event at the magnetopause. Similar magnetic field and electric current behavior between each spacecraft indicates the formation of a quasi 2D structure. However, we find that the energy dissipation results of each spacecraft are different. Further analysis indicates that the reconnection electric field, E_M, plays a key role in this process. Thus, we suggest that the energy dissipation of magnetic reconnection is unsteady on this spatial or temporal scale, even under stable diffusion conditions.

How to cite: Dong, X., Dunlop, M., Wang, T., Giles, B., Torbert, R., Russell, C., and Burch, J.: Unsteady energy dissipation in the magnetic reconnection diffusion region, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8780, https://doi.org/10.5194/egusphere-egu2020-8780, 2020.

We analyze in detail a reconnection site observed by the Magnetospheric Multiscale (MMS) mission in the magnetotail. The interval around the X-line is identified based on the ion jet reversal, Hall electric fields and other reconnection signatures. At the reconnection site strong electric fields with amplitudes above 100mV/m are observed. In addition, the region shows strong turbulent variations on ion scales, including magnetic island-like structures. We discuss the cause of strong electric fields, their relation to ion scale structures and associated particle acceleration in this region. Of particular interest is the relation of the reconnection site to the generation of kinetic Alfven waves.

How to cite: Vaivads, A., Liu, C., Khotyaintsev, Y. V., Graham, D. B., Lindqvist, P.-A., Torbert, R. B., Burch, J. L., Russell, C. T., Contel, O. L., Giles, B. L., and Gershman, D. J.: Reconnection site and ion scale turbulence generation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11451, https://doi.org/10.5194/egusphere-egu2020-11451, 2020.

The typical picture of magnetic reconnection in the magnetosphere includes a classic Harris-type current sheet, where the current density is maximum at the magnetic equator (Bx=0). However, observations have shown that the magnetotail current sheet structure is much more complicated than this simple view. Therefore, revealing the structure of the current sheet is of importance to understand the reconnection process. Based on the four-point MMS high-resolution data, we present observations of a multiple reconnection event for which we study the structure of the current sheet as well as some of its characteristic scales. We show that the CS structure is highly dynamic during the reconnection process, changing from a bifurcated shape away from the reconnection site, to a more symmetric (Harris-type) structure near the X-line.

How to cite: Rojas Castillo, D., Nakamura, R., and Nakamura, T. K. M.: Current sheet structure close to a reconnection point observed by MMS, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13506, https://doi.org/10.5194/egusphere-egu2020-13506, 2020.

Magnetosheath jets are local enhancements of dynamic pressure above the background level. Hietala et al. (2018) recently presented observational evidence of a jet collision with the magnetopause causing magnetic field line reconnection. In the present study, we show data which, for the first time, strongly indicates that magnetosheath jets can even create localized transient reconnection events, so-called flux transfer events (FTEs).

FTEs are commonly observed in cascades with an average separation time of 8-10 minutes, but may also appear as isolated events. Despite the fact that FTEs have gained major attraction during recent years, the formation process of FTEs is not yet fully understood. We showed in a recent statistical study (Kullen, Thor, and Karlsson; 2019) that isolated FTEs and FTE cascades occur during different IMF conditions and are differently distributed along the magnetopause. The results of the statistical study strongly suggest that the majority of the FTEs formed along the expected reconnection region for each respective IMF condition. However, for a subset of isolated FTEs, we proposed a different formation process. These events may have been caused by magnetosheath jets, as they occur during IMF conditions favorable for jet formation. Simulation results by Karimabadi et al. (2014) has shown that such a creation mechanism is possible. In his simulation, a magnetosheath jet collides with the magnetopause, creating an FTE.

In the present investigation, FTEs that may have been caused by magnetosheath jets were identified. To achieve this, we examined measurements from all four Cluster satellites, and searched for magnetosheath jets that appear in close proximity to FTEs listed in Wang et al. (2005)’s FTE list. Our results show that approximately 15% of isolated FTEs appear in the vicinity of jets. These FTEs are further examined based on IMF and location across the magnetopause. For two of the FTEs, the associated jet appears close to the magnetopause. We present a detailed data analysis of these two events and discuss a possible formation mechanism for the FTEs, as there is strong evidence that the two FTEs are indeed caused by jets.

How to cite: Thor, S., Kullen, A., Karlsson, T., and Raptis, S.: First Evidence of Flux Transfer Events Caused by Mangetosheath Jets, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-811, https://doi.org/10.5194/egusphere-egu2020-811, 2020.

Using measurements by the Magnetospheric Multiscale (MMS) spacecraft in the magnetotail, we studied electron distribution functions across an electron diffusion region. The dependence of the non-gyrotropic distribution on the energy and vertical distance from the EDR mid-plane was revealed for the first time. The non-gyrotropic distribution was observed everywhere except for an extremely narrow layer right at the EDR mid-plane. The energy of the non-gyrotropic distribution increased with growth of the vertical distance from the mid-plane. For the electrons within certain energy range, they exhibited the non-gyrotropic distribution at the distance further away from the mid-plane than that expected from the meandering motion. The correlation between the crescent-shaped distribution with multiple stripes and the large Hall electric field was established. It appears that the measured non-gyrotropic distribution and the crescent-shaped distribution were caused by the meandering motion and the Hall electric field together.

How to cite: Li, X. and Lu, Q.: Observation of non-gyrotropic electron distribution across the electron diffusion region in the magnetotail reconnection, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1549, https://doi.org/10.5194/egusphere-egu2020-1549, 2020.

Magnetic reconnection is a fundamental plasma process, by which magnetic energy is explosively released in the current sheet to energize charged particles and to create bi-directional Alfvénic plasma jets. A long-outstanding issue is how the stored magnetic energy is rapidly released in the process. Numerical simulations and observations show that formation and interaction of magnetic flux ropes dominate the evolution of the reconnecting current sheet. Accordingly, most volume of the reconnecting current sheet is occupied by the flux ropes and energy dissipation primarily occurs along their edges via the flux rope coalescence. Here, for the first time, we present in-situ evidence of magnetic reconnection inside the filamentary currents which was driven possibly by electron vortices inside the flux ropes. Our results reveal an important new way for energy dissipation in magnetic reconnection.

How to cite: Wang, S. and Lu, Q.: Direct evidence of secondary reconnection inside filamentary currents of magnetic flux ropes in magnetic reconnection, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1671, https://doi.org/10.5194/egusphere-egu2020-1671, 2020.

Can reconnection be triggered as a directional discontinuity (DD) crosses the bow shock? Here we present some unique observations of asymmetric reconnection at a quasi-perpendicular bow shock as an interplanetary DD is crossing it simultaneously with the Magnetospheric Multiscale (MMS) mission. The data show indications of ongoing reconnection at the bow shock southward of the spacecraft. The DD is also observed by several upstream spacecraft (ACE, WIND, Geotail, and THEMIS B) and one downstream in the magnetosheath (Cluster 4), but none of them resolve signatures of ongoing reconnection. We therefore suggest that reconnection was temporarily triggered as the DD was compressed by the shock. Bow shock reconnection is inevitably asymmetric with both the density and the magnetic field strength being higher on one side of the X-line (the magneosheath side) than on the other side where the plasma flow also is supersonic (the solar wind side). Asymmetric reconnection of the bow shock type has never been studied before, and the data discussed here are hence unique.

How to cite: Gunell, H., Hamrin, M., Goncharov, O., De Spiegeleer, A., Fuselier, S., Mukherjee, J., and Vaivads, A.: Asymmetric reconnection at the bow shock, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4750, https://doi.org/10.5194/egusphere-egu2020-4750, 2020.

How to cite: Lenouvel, Q., Génot, V., Garnier, P., Toledo-Redondo, S., Lavraud, B., Torbert, R., Giles, B., and Burch, J.: On the identification of Electron Diffusion Regions at the magnetopause with an AI approach, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9881, https://doi.org/10.5194/egusphere-egu2020-9881, 2020.

Magnetic reconnection is a mechanism that allows rapid and explosive energy transfer from the magnetic field to the plasma. The magnetopause is the interface between the shocked solar wind plasma and Earth’s magnetosphere. Reconnection enables the transport of momentum from the solar wind into Earth’s magnetosphere. Because of its importance in this regard, magnetic reconnection has been extensively studied in the past and is the primary goal of the ongoing Magnetospheric Multiscale (MMS) mission. During magnetic reconnection, the originally anti-parallel fields annihilate and reconnect in a thinned current sheet. In the vicinity of a reconnection site, a prominently increased curvature of the magnetic field (and smaller radius of curvature) marks the region where the particles start to deviate from their regular gyro-motion and become available for energy conversion. Before MMS, there were no closely separated multi-spacecraft missions capable of resolving these micro-scale curvature features, nor examining particle dynamics with sufficiently fast cadence.

In this study, we use measurements from the four MMS spacecraft to determine the curvature of the field lines and the plasma properties near the reconnection site. We use this method to study FTEs (flux ropes) on the magnetopause, and the interaction between co-existing FTEs. Our study not only improves our understanding of magnetic reconnection, but also resolves the relationship between FTEs and structures on the magnetopause.

How to cite: Qi, Y., Russell, C. T., Strangeway, R. J., Jia, Y., Torbert, R. B., Paterson, W. R., Giles, B. L., and Burch, J. L.: Magnetic Curvature Analysis on Reconnection Related Structures at Earth’s Magnetopause, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3764, https://doi.org/10.5194/egusphere-egu2020-3764, 2020.