Magnetospheric Multiscale (MMS) MissionCopyright (c) 2023 Embry-Riddle Aeronautical University All rights reserved.
https://commons.erau.edu/mms-conference
Recent documents in Magnetospheric Multiscale (MMS) Missionen-usFri, 03 Feb 2023 10:37:01 PST3600Identification of magnetotail current sheets with MMS magnetometer data based on a moving average algorithm
https://commons.erau.edu/mms-conference/2022/tuesday/44
https://commons.erau.edu/mms-conference/2022/tuesday/44Tue, 10 May 2022 17:30:00 PDT
The dynamics of the magnetotail current sheet is important to understanding particle acceleration in the Earth’s magnetosphere. Thin current sheets associated with intermittent plasma turbulence, together with high-amplitude electric fields, have been posed as essential ingredients for strong local heating (Stawarz et al. 2015; Ergun et al. 2020). Several statistical studies have been done in the magnetosheath (Chasapis et al., 2017) and in bursty bulk flow (BBF) braking regions (Ergun et al., 2015). These studies employ either the Partial Variance of Increments (PVI) of the magnetic field, or large-amplitude (>50 mV/m) electric fields. However, observations in the distant tail often reveal large-amplitude, spiky electric fields in both lobe-like and sheet-like B fields, which may be associated with either boundary layer plasma mixing or processes related to reconnection. Also, the flapping motion of the tail frequently results in brief lobe and sheet excursion on many temporal scales. Thus, this calls for a multiscale categorization of the processes associated with the lobe and plasma sheet. Previous surveys of lobe-like or sheet-like magnetic fields are often performed with fixed thresholds (Jackman & Arridge, 2011; Coxon et al., 2016) or fitting models (Fairfield & Jones, 1996; Nakamura et al., 2006). PVI search methods, although based on relative calculations, are also dependent on a choice of temporal/spatial scale. Thus, we present a search algorithm based on moving averages of the magnetic field and PVI scalograms to flexibly differentiate lobe/sheet-like fields, which results in a database for future statistical studies. We also present a preliminary survey of the magnetic and electric fields profile in the lobe and current sheet. For future studies, this might be correlated with particle measurements to establish a relation between energy transport between the field and various processes associated with turbulence or reconnection in the magnetotail.
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Tien VoHORNET - A New Measure of Kinetic-Scale Energy Conversion
https://commons.erau.edu/mms-conference/2022/friday/25
https://commons.erau.edu/mms-conference/2022/friday/25Fri, 13 May 2022 16:00:00 PDT
Kinetic-scale energy conversion and dissipation play a crucial role in the dynamics of magnetic reconnection and turbulence. The pressure-strain interaction recently reintroduced [Y. Yang et al., Phys.Plasmas 24, 072306 (2017)] is the only channel for energy conversion into internal energy and compression (because heat flux has no net contribution); it has thus been employed as a diagnostic in numerical simulations of reconnection and turbulence and in satellite observations to identify the power density of plasma heating or cooling. The pressure-strain interaction term can be decomposed into pressure dilatation which deals with the conversion of energy due to compression (changing the density) and Pi-D which describes incompressible conversion to or from internal energy (changing the temperature). We present a new measure on the same footing as the pressure-strain interaction dubbed “higher order non-equilibrium term” (HORNET), which gives the power density of energy conversion to all moments of the phase space density beyond temperature, thus describing energy going into changing the shape of the phase space density. We perform particle-in-cell simulations of symmetric magnetic reconnection and compare HORNET to the pressure-strain and heat flux terms. We find that HORNET identifies regions where kinetic-scale energy conversion is taking place and we find that energy going into higher order moments can be a significant fraction of the total energy conversion in and near the diffusion region. We furthermore show that while the heat flux divergence does not contribute to the net heating, it can be important locally and can even dominate over Pi-D.
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M. Hasan Barbhuiya et al.Using MMS multi-spacecraft data for the determination of photon mass and Lorentz-Poincaré symmetry violation
https://commons.erau.edu/mms-conference/2022/friday/24
https://commons.erau.edu/mms-conference/2022/friday/24Fri, 13 May 2022 15:45:00 PDT
The photon is commonly believed being the only free massless particle. Deviations from the Ampère-Maxwell law, due to a photon mass, real for the de Broglie-Proca theory, or effective for the Lorentz-Poincaré Symmetry Violation (LSV) in the Standard-Model Extension (SME) were sought in six years of MMS satellite data. In a minority of cases (but mostly in the solar wind: 8.6% for the modulus and 16.8% for the Cartesian components for top-quality burst data and best tetrahedron configurations), deviations have been found. After error analysis, the minimum photon mass value would be 1.74×10^{−}^{53} kg while the LSV parameter |k_{AF}| would be 4.95×10^{−}^{11} m^{−}^{1}. Future satellite measurements may clarify the nature of these deviations, whether unaccounted errors or profoundly meaningful deviations.
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Alessandro SpallicciStrong reconnection electric fields in electron-only reconnection and regular reconnection in shock-driven turbulence
https://commons.erau.edu/mms-conference/2022/friday/22
https://commons.erau.edu/mms-conference/2022/friday/22Fri, 13 May 2022 15:15:00 PDT
In the Earth’s quasi-parallel bow shock, shock-driven turbulence generates current sheets, and MMS has been observing both electron-only reconnection, where only electron jets are generated, and regular reconnection, where both ion jets and electron jets are generated. To investigate the reconnection electric fields in shock-driven turbulence in the Earth’s bow shock, we performed 2D particle-in-cell simulations. In this presentation, we will discuss that the reconnection electric field in shock-driven reconnection is unusually larger than the prediction of the reconnection electric field in the standard laminar reconnection. In electron-only reconnection, the outflow speed reaches local electron Alfven speed. In some electron-only reconnection regions, only a one-sided electron jet is generated, and the region in the other side becomes an additional inflow region. We demonstrate that the outflow speed in such an unusual one-sided jet also reaches of the order of electron Alfven speed. In regular reconnection, the ion outflow speed also becomes 10 times the Alfven speed due to the ion reflection by the shock. As a result of the high speed jet, the convection electric field due to the outflows becomes a square root of the mass ratio times larger than that in the standard laminar reconnection, and the reconnection electric field reaches the same order. MMS observations of electron-only reconnection in the Earth’s magnetosheath show that electron outflow jets reach of the order of electron Alfven speed, and the reconnection electric field becomes much larger than the prediction in the standard laminar reconnection.
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Naoki Bessho et al.Measures of correlation length at quasi-parallel and quasi-perpendicular shocks
https://commons.erau.edu/mms-conference/2022/friday/21
https://commons.erau.edu/mms-conference/2022/friday/21Fri, 13 May 2022 15:00:00 PDT
The solar wind and magnetosheath are known to be turbulent plasmas containing an energy cascade across a wide range of scales, the largest of which is the stirring scale. From recent observations and simulations of Earth’s bow shock, we have seen that there is a disordered or turbulent transition region containing reconnecting current sheets. This raises two key questions: Is there a link between the turbulent reconnection observed in the magnetosheath and the shock? How do properties of the turbulence, such as the stirring scale, evolve as solar wind plasma crosses the bow shock? We present two case studies of quasi-parallel and quasi-perpendicular bow shock crossings observed by Magnetospheric Multiscale (MMS). We measure changes in the stirring scale of the turbulence through the bow shock using combined magnetic field measurements from both the flux gate (FGM) and search coil (SCM) magnetometers. The stirring scale is quantified using the correlation length, where the influence of the shock ramp is reduced using a high pass filter. We find that the bow shock transition region is coincident with a reduction in peak correlation length by an approximate factor of ten, while the average correlation length is approximately halved compared to the solar wind closely preceding the shock.
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James Plank et al.Observational Verification of the Electron Vlasov Equation with MMS
https://commons.erau.edu/mms-conference/2022/friday/20
https://commons.erau.edu/mms-conference/2022/friday/20Fri, 13 May 2022 14:45:00 PDT
The Fast Plasma Investigation (FPI) onboard NASA’s Magnetospheric Multiscale (MMS) four-spacecraft mission constitutes an historic advance in plasma physics particle detection capabilities. As a result of the unprecedented temporal, spatial, and velocity-space resolution offered by the suite of dual electron spectrometers (DES), MMS is capable of directly measuring the velocity-space structure of terms in the electron Vlasov equation as demonstrated by Shuster et al. [2021] for electron-scale current layers observed near Earth’s dayside reconnecting magnetopause. In this work, we present MMS observations of all three terms in the electron Vlasov equation: the temporal derivative term ∂f_{e}/∂t, the spatial gradient term v⋅∇f_{e}, and the velocity-space gradient term (F/m_{e})⋅∇_{v}f_{e}. We discuss various applications, implications, and limitations of our methodology. The immediate advantage of multipoint measurements is the ability to distinguish between temporal and spatial variations in the plasma; both a thin, slow-moving structure and a thick, fast-moving one would produce the same measured time series of a quantity when sampled at only a single spatial location. FPI offers a novel way to infer spatiotemporal variations of the plasma from a single spacecraft: careful measurement of how the shape of the plasma’s distribution function f_{e}(v) changes via the velocity-space gradient term ∇_{v}f_{e} yields qualitatively similar velocity-space structures as those captured by ∂f_{e}/∂t and the four-spacecraft measurement of v⋅∇f_{e}. Making use of ∂f_{e}/∂t for steady-state structures, we obtain a higher spatially-resolved (~1 to 3 km) single-spacecraft version of the parallel component of the electron pressure divergence (∇⋅P_{e})_{//} that exhibits agreement with the parallel electric field measured by the electric field double probes (EDP), whereas the standard four-spacecraft method for computing ∇⋅P_{e} cannot capture spatial variations smaller than the spacecraft separation (~10 km). Just as v⋅∇f_{e} offers a kinetic perspective into the origins of ∇⋅P_{e}, the (F/m_{e})⋅∇_{v}f_{e} term offers an analogous velocity-space perspective into the energy conversion term J⋅E’ whenever J can be approximated by J_{e} = −en_{e}U_{e}, which is often the case for electron-scale structures. Thus, these results are immediately relevant to the study of fundamentally kinetic energy conversion processes, including electron diffusion regions (EDRs) fueling magnetic reconnection, kinetic-scale turbulence, and wave-particle interactions such as those believed to be consistent with Landau damping as inferred from recently reported velocity-space signatures using MMS data from the turbulent magnetosheath.
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Jason Shuster et al.A New Theory of Kinetic-Scale Energy Conversion and Dissipation
https://commons.erau.edu/mms-conference/2022/friday/19
https://commons.erau.edu/mms-conference/2022/friday/19Fri, 13 May 2022 14:30:00 PDT
The Magnetospheric Multiscale (MMS) mission has enabled research into kinetic-scale energy conversion and dissipation in exquisite detail. Studying energy conversion is complicated where collisions are extremely weak, leading to systems far from local thermodynamic equilibrium (LTE). Recently, the crucial role played by non-LTE effects in impacting the evolution of plasma temperature has been emphasized [Y. Yang et al., Phys. Plasmas, 24, 072306 (2017)]. The key non-LTE term is known as Pi-D, which appears in the temperature evolution equation. In this study, we show the temperature evolution equation is incomplete, missing key kinetic physics that can play an important role in energy conversion. We argue that energy conversion can be thought of as a hierarchy of changes to all moments of the phase space density. Work due to compression changes the zeroth moment (density), while Pi-D and heat flux change the second moment (temperature); both are described by the temperature evolution equation. However, the equation is agnostic to changes to any higher order moment. We develop a new paradigm to describe these manifestly non-LTE kinetic effects. Using entropy defined in kinetic theory, we derive an energy evolution equation that supplants the first law of thermodynamics – we dub it “the first law of kinetic theory.” We show this law retains all information described by the temperature evolution equation, in addition to describing energy conversion to all higher order moments. We compare and contrast amplitudes and profiles of terms in the first law of kinetic theory in particle-in-cell simulations of symmetric magnetic reconnection.
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Paul Cassak et al.Energy conversion through various channels in turbulent plasmas induced by the Kelvin-Helmholtz instability at the Earth’s magnetopause
https://commons.erau.edu/mms-conference/2022/friday/17
https://commons.erau.edu/mms-conference/2022/friday/17Fri, 13 May 2022 14:00:00 PDT
Energy conversion in collisionless plasmas is central to the plasma heating and particle energization problems in space and astrophysical plasmas, which remain unsolved nowadays. Though it is known that the electromagnetic energy is converted to the flow and random kinetic energy (via J.E), a detailed understanding of how the electromagnetic energy is converted into particle energy and finally dissipated to heat is still lacking. Motivated by the rich physics of Kelvin-Helmholtz (KH) waves, we consider energy conversion in turbulent plasmas induced by the KH instability at the Earth’s magnetopause. With observations from the Magnetospheric Multiscale mission, we consider the energy conversion from (1) the electromagnetic fields into the flow and (2) from the flow into thermal energy for each plasma species through the pressure work (via P.∇.v). We find that the KH vortex regions, where the magnetospheric and magnetosheath plasmas mix, are the key sites of energy conversion activities. Considering the accumulation of the energy conversion through various channels with time, we find that the accumulated energy conversion rate through the electromagnetic channel constantly increases. However, the accumulated energy conversion rate through the pressure work channel only increases when the KH waves reach the nonlinear stage of development. Moreover, while the energy conversion between flow and heat via P.∇.v is very dynamic for electrons, we find that the main contribution, which finally dissipates the flow energy into heat, comes from ions. By separating the contributions of J.E and P.∇.v into multiple terms, we will discuss kinetic processes that are likely responsible for the energy conversion. We will also discuss the partitioning of energy conversion through the different channels for each species. This work paves the way towards an understanding of energy transfer across scales in turbulent plasmas as mediated by magnetopause KH waves.
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Rungployphan KieokaewStudy of slow-mode shocks in magnetic reconnection based on hybrid simulations and satellite observations
https://commons.erau.edu/mms-conference/2022/friday/16
https://commons.erau.edu/mms-conference/2022/friday/16Fri, 13 May 2022 13:45:00 PDT
Petschek’s model of reconnection has reconnection rate comparable to in-situ observations, and it has a small diffusion region which is flanked by two slow-mode shocks on each side of the exhaust. This study explores the existence of slow-mode shocks in magnetic reconnection with both 2.5 D hybrid simulations and Magnetospheric MultiScale (MMS) observations. We use the six Rankine-Hugoniot conditions and the six specific conditions for slow-mode shocks to analyze the presence of slow-mode shocks in both simulations and in-situ satellite observations. We observe that the reconnection boundary can be interpreted as a slow-mode shock from as close as ~9 ion inertial lengths from the X-point. The detection of slow-mode shocks increases with increasing distance from the X-point and with increasing ion plasma beta [Walia et. al., 2022]. The change in beta leads to the change in turbulence, thus causing a decrease in the detection of slow-mode shocks as the turbulence increases. Some dependence of occurrence of slow-mode shocks is also found on the ion to electron pressure ratio. Additionally, we observe that if the slow-mode shocks are analyzed by taking artificial satellite cuts in the simulations at various angles, the detection percentage of slow-mode shocks can decrease to ∼10% for very oblique crossings. In the near-Earth magnetotail crossings of MMS, 28 out of 51 crossings are observed to have slow-mode shocks. The number of detections of slow-mode shocks in the near-Earth magnetotail (55%), and in hybrid simulations, suggests that they are a prominent part of magnetic reconnection geometry.
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Nehpreet K. Walia et al.Measurements of nongyrotropic electrons around the cyclotron resonance velocity in whistler-mode waves
https://commons.erau.edu/mms-conference/2022/friday/15
https://commons.erau.edu/mms-conference/2022/friday/15Fri, 13 May 2022 13:30:00 PDT
The interaction between the electromagnetic field and charged particles is central for the collisionless plasma dynamics in space. Whistler-mode waves are one of the electromagnetic plasma waves, which play important roles in efficient pitch-angle scattering and acceleration of electrons in solar wind, collisionless shock waves as well as planetary magnetospheres. The nonlinear wave-particle interaction theory for coherent large amplitude waves predicts that electrons around resonance velocities exhibit nongyrotropy due to the phase trapping motion around them and the nongyrotropic electrons exchange energy and momentum with the waves in the presence of an appropriate inhomogeneity. In this presentation, we show observational results of nongyrotropic electrons around the cyclotron resonance velocity using the data obtained by the Magnetospheric Multiscale (MMS) spacecraft during a whistler-mode wave (about 200 Hz) event around the magnetosheath-side separatrix of the dayside magnetopause reconnection. On the basis of measurements by the Fast Plasma Investigation Dual Electron Spectrometer (FPI-DES), the search-coil magnetometer (SCM), and the Electron Drift Instruments (EDI), the relative phase angle of the electron hole to the magnetic field of the whistler-mode wave agrees well with the prediction by the nonlinear theory, and this type of the electrons appeared only around the cyclotron resonance velocity. The electron flux at the hole was about 40% lower than that at the peak in the most pronounced case. This result provides evidence of locally ongoing nonlinear wave-particle interaction between the electrons and whistler-mode waves, and proves that the nonlinear wave growth occurs around the dayside reconnection.
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Naritoshi Kitamura et al.Formation of double layers during magnetic reconnection in the presence of flat-top distributions of particles: Theory and observations
https://commons.erau.edu/mms-conference/2022/friday/14
https://commons.erau.edu/mms-conference/2022/friday/14Fri, 13 May 2022 13:15:00 PDT
Several satellite missions have confirmed the existence of unipolar parallel electric fields in various regions of the terrestrial magnetosphere, including the plasma sheet region, the auroral region, and the magnetopause/magnetotail reconnection sites. Recently, Magnetospheric Multiscale (MMS) mission observed parallel electric field fluctuations up to 100 mV/m at the magnetic reconnection site of the Earth's magnetopause. These parallel electric fields are interpreted as double layers (DLs), which may cause secondary reconnection. Furthermore, DLs may occur within the reconnection exhaust, regulating the partitioning of the released magnetic energy during magnetic reconnection. In addition to DLs, particle distributions with superthermal tails and shoulders (flat-top distribution) have been reported in the literature based on MMS data. Motivated by the reported literature, we investigate DLs and their associated electric fields at the magnetopause magnetic reconnection site by using a simple analytical model in which the DLs associated with kinetic Alfvén waves are examined in a two-component flat-top distributed plasma. The flat-top distribution affects the DL's strength (as defined by the potential drop) and its associated parallel electric field. Our findings are consistent with previous research on DLs in the Earth's magnetosphere. Additionally, we discuss the implications of our findings on charged particle energization in the separatrix region of the Earth's magnetosphere using MMS data.
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Muhammad Shamir et al.Statistical Study of Shock Non-Stationarity
https://commons.erau.edu/mms-conference/2022/friday/12
https://commons.erau.edu/mms-conference/2022/friday/12Fri, 13 May 2022 11:45:00 PDT
Owing to the high temporal resolutions of FPI/DIS, MMS can resolve the fine structure of the shock ramp, which often shows presence of holes in reduced ion-phase space distributions (integrated along the tangential plane of the shock). Such holes have been associated with rippling propagating along the shock surface, but also have been observed in association with the shock reformation. In this study, we have focused on characterizing ion phase-space holes at the Earth’s bow shock using MMS observations. We use a machine learning approach to automatically identify shock crossings using the FPI/DIS data. We compile a database of those crossings including various spacecraft-related and shock-related parameters for each event. We select ~500 shock crossings with burst data and establish a systematic procedure to find the shocks exhibiting phase space holes. We characterize the occurrence of the holes as a function of shock parameters such as Mach number and geometry. These results are important to understanding the non-stationary behavior of collisionless shocks.
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Yuri Khotyaintsev et al.The Success of MMS in Characterizing Electron Diffusion Regions During Reconnection in the Earth’s Magnetosphere.
https://commons.erau.edu/mms-conference/2022/friday/11
https://commons.erau.edu/mms-conference/2022/friday/11Fri, 13 May 2022 11:30:00 PDT
A major science goal of the MMS mission is “to reveal, for the first time, the small-scale three-dimensional structure and dynamics of the elusively thin and fast-moving electron diffusion region”. The mission has been hugely successful in accomplishing this goal, where remarkable and detailed data have been obtained for a large number of electron diffusion regions (EDRs) encounters. In this talk I will review results for three of the perhaps most studied EDRs [1,2,3]. First, in the dayside magnetopause strong density asymmetries yield crescent shaped features in the electron velocity distributions [1] over a range along the topological separator [4], whereas within the EDR the frozen-in-law is broken by dynamics of oblique electron beams [5]. In the Earth magnetotail, perfectly symmetric and anti-parallel reconnection has been observed [2], which permitted a direct evaluation of the off-diagonal electron pressure stress elements responsible for reconnection [6]. Reconnection with a weak guide-field has also been observed [3], which together with trapped electron dynamics and associated electron pressure anisotropy impact the Regime-type of the EDR [7,8].
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Jan EgedalTest of accuracy of polynomial reconstruction and reconstruction of an event without MMS4 current density
https://commons.erau.edu/mms-conference/2022/friday/10
https://commons.erau.edu/mms-conference/2022/friday/10Fri, 13 May 2022 11:15:00 PDT
Our polynomial reconstruction technique uses input from the magnetic field and particle current density measured by the MMS spacecraft to find a quadratic model for the magnetic field. First we extend our technique by using input data from multiple observation times. This extension yields somewhat more accurate reconstructions and also yields an estimate of the structure velocity. Then we test the accuracy of reconstructions by reconstructing the magnetic field in a three-dimensional particle in cell simulation, using virtual spacecraft data as input to the reconstruction. The results are heavily influenced by the amount of temporal smoothing of the input data. More smoothing allows a qualitatively more accurate reconstruction, but the resulting reconstruction then represents spatially smoothed simulation fields with time variation at timescales less than the smoothing time excluded. Reconstruction of a magnetotail reconnection event observed by MMS on 27 August 2018, when the MMS4 current density was unavailable, yields a reconstruction consistent with the previous interpretation by Li et al. (2021) based on the time-dependent data.
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Richard E. Denton et al.Energy transfer and proton-electron heating in turbulent plasmas
https://commons.erau.edu/mms-conference/2022/friday/9
https://commons.erau.edu/mms-conference/2022/friday/9Fri, 13 May 2022 11:00:00 PDT
Despite decades of study of high-temperature weakly-collisional plasmas, a complete understanding of how energy is transferred between particles and fields remains elusive. Two major questions in this regard are how fluid-scale energy transfer rates, associated with turbulence, connect with kinetic-scale dissipation, and what controls the fraction of dissipation on different charged species. Although the rate of cascade has long been recognized as a limiting factor in the heating rate at kinetic scale, no study has reported direct evidence correlating the heating rate with MHD-scale cascade rates. Using kinetic simulations and in-situ spacecraft data, we show the connection between the fluid-scale energy flux and the total energy dissipated at kinetic scales. The proton versus electron heating is controlled by the ratio of non-linear time scale to the proton-cyclotron time and increases with the total dissipation rate. These results advance a key step toward understanding dissipation of turbulent energy in collisionless plasmas.
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Riddhi Bandyopadhyay et al.