Search

High resolution observations of dense plasma impulsive structures moving through an ambient background magnetospheric flows were captured by the Magnetospheric Multiscale mission. The observations show particle heating and acceleration, shock‐like wave formation, and whistler wave excitation inside the interface between the dense impulsive plasma structures and the ambient plasma. A multiscale hybrid kinetic simulation provides an explanation of the observed wave‐particle interactions with the assumption that the dense plasma structures may be represented by plasma clouds which are formed at the magnetopause layer due to reconnection processes. Plain Language Summary: Dense, impulsive plasma structures moving through a background plasma were captured by the NASA Magnetospheric Multiscale mission. The observations show that the dense structures can generate strong perturbations in the electromagnetic field and shock‐like waves. Interactions between these electromagnetic waves and the particles results in particle acceleration. 3‐D hybrid kinetic modeling (particle description for ions and fluid description for electrons) was used to investigate the plasma physics of the observed structures. It was assumed that the plasma clouds were formed by magnetic field reconnection inside the magnetopause, which is the interface between the solar wind particles and the cold low‐density magnetospheric plasma. The work helps us understand the plasma environment at the interface between the Earth and solar wind, near planetary moons, within astrophysical explosions, and possibly at the interface between the solar wind and local interstellar medium. Key Points: MMS has captured high‐resolution observations of dense plasma structures moving through sub‐Alfvenic and supersonic ambient background magnetospheric flowsStrong acceleration of the ambient ions are observed at the interface between the plasma structure and the background plasmaThe observations, combined with hybrid kinetic modeling, provide for the first time insights into the physics of wave‐particle interactions triggered by dense impulsive structures moving through background plasmas [ABSTRACT FROM AUTHOR]

The stability of microchannel plate (MCP) gain with time impacts the success of long-term space plasma missions that use such detectors. Gain stability is of particular importance for the Fast Plasma Investigation (FPI) suite on NASA's Magnetospheric Multiscale (MMS) mission, which operates 64 independent MCP assemblies. Due to this massive number of sensors, there was not sufficient time to fully precondition all flight detectors prior to MMS launch. Therefore, an understanding of the change of MCP gain with time is vital to ensure quality FPI performance. We have conducted lifetime experiments with flight-grade FPI-like MCP assemblies for both ion and electron detectors. These experiments demonstrate that MCP gain stabilizes after ≈ 1.0 C/ c m 2 has been extracted from the plates. Based on these results, the FPI MCPs could potentially operate for 20+ years on-orbit. [ABSTRACT FROM AUTHOR]

The article discusses the principle of operation and the testing of a panoramic plasma spectrometer which is a miniature electro-optic system that guarantees 2π field of view with a single coordinate-sensitive detector. Basically, this is an all-sky camera for charged particles. The feed optics can be adjusted for specific conditions of experiments and for various analyzers of the second stage.

In this paper we use Interball-tail observations and numerical modeling to investigate ion acceleration in reconnected nightside magnetopause. We consider magnetic field configuration corresponding to the superposition of the magnetopause current sheet and reconnected fluxtube, which moves tailward. This fluxtube creates normal component of the magnetic field and the transverse electric field component. Initial current sheet geometry includes tangential and shear components of the magnetic field. Interaction of cold magnetosheath ions with the reconnected current sheet results in particle acceleration and transition through the magnetopause. Reflected and transited ions form velocity distributions with a halo in the ( v ‖ , v ⊥ ) plane. Numerical modeling reproduce these velocity distributions quite well. Comparison of numerical results and spacecraft observation indicates that nonadibatic ion acceleration plays essential role in formation of such velocity distributions. [ABSTRACT FROM AUTHOR]

We investigate the dynamics of Earth's quasi-parallel terrestrial bow shock based on measurements from the Magnetospheric MultiScale (MMS) spacecraft constellation during a period of near-radial interplanetary magnetic conditions, when the interplanetary magnetic field and the solar wind (SW) velocity are nearly anti-parallel. High-speed earthward ion flows with properties that are similar to those of the pristine SW are observed to be embedded within the magnetosheath-like plasma. These flows are accompanied by Interplanetary Magnetic Field (IMF) intensity of less than about 10 nT, compared to nearby magnetosheath intensities of generally greater than 10 nT. The high-speed flow intervals are bounded at their leading and trailing edges by intense fluxes of more energetic ions and large amplitude quasi-sinusoidal magnetic oscillations, similar to ultra-low frequency waves known to steepen and pileup on approach toward Earth to form the quasi-parallel bow shock. The MMS string-of-pearls configuration is aligned with the outbound trajectory and provides inter-spacecraft separations of several hundred km along its near 103 length, allowing sequential observation of the plasma and magnetic field signatures during the event by the four spacecraft. The SW-like interval is most distinct at the outer-most MMS-2 and sequentially less distinct at each of the trailing MMS spacecraft. We discuss the interpretation of this event alternatively as MMS having observed a quasi-rigid bow shock contraction/expansion cycle, ripples or undulations propagating on the bow shock surface, or a more spatially local evolution in the context of either a deeply deformed shock surface or a porous shock surface, as in the three-dimensional patchwork concept of the quasi-parallel bow shock, under the extant near-radial IMF condition. [ABSTRACT FROM AUTHOR]

The deviation from thermodynamic equilibrium of the ion velocity distribution functions (VDFs), as measured by the Magnetospheric Multiscale (MMS) mission in the Earth's turbulent magnetosheath, is quantitatively investigated. Making use of the unprecedented high-resolution MMS ion data, and together with Vlasov–Maxwell simulations, this analysis aims at investigating the relationship between deviation from Maxwellian equilibrium and typical plasma parameters. Correlations of the non-Maxwellian features with plasma quantities such as electric fields, ion temperature, current density and ion vorticity are found to be similar in magnetosheath data and numerical experiments, with a poor correlation between distortions of ion VDFs and current density, evidence that questions the occurrence of VDF departure from Maxwellian at the current density peaks. Moreover, strong correlation has been observed with the magnitude of the electric field in the turbulent magnetosheath, while a certain degree of correlation has been found in the numerical simulations and during a magnetopause crossing by MMS. This work could help shed light on the influence of electrostatic waves on the distortion of the ion VDFs in space turbulent plasmas. [ABSTRACT FROM AUTHOR]

We investigate the kinetic structure of electron‐scale current sheets found in the vicinity of the magnetopause and embedded in the magnetosheath within the reconnection exhaust. A new technique for computing terms of the Vlasov equation using Magnetospheric Multiscale (MMS) measurements is presented and applied to study phase space density gradients and the kinetic origins of the electron pressure divergence found within these current sheets. Crescent‐shaped structures in ∇⊥2fe give rise to bipolar and quadrupolar signatures in v·∇fe measured near the maximum ∇·Pe inside the current layers. The current density perpendicular to the magnetic field is strong (J⊥∼2 μA/m2), and the thickness of the current layers ranges from 3 to 5 electron inertial lengths. The electron flows supporting the current layers mainly result from the combination of E×B and diamagnetic drifts. We find nonzero J·E′ within the current sheets even though they are observed apart from typical diffusion region signatures. Plain Language Summary: We discovered how to use data from outer space to measure what is known as the Vlasov equation, held by many to be the most important equation in plasma physics. Beginning with Ludwig Boltzmann's insights from the late 1800s regarding microscopic motions of ordinary gases, Anatoly Vlasov in 1945 applied Boltzmann's ideas to understand the nature of electrified gases called plasmas. What has prevented researchers from measuring the Vlasov equation for over 100 years since Boltzmann? The difficulty is that Vlasov's equation lives in phase space, which enlists no less than seven dimensions — three for position (x, y, z), three for velocity (vx, vy, vz), and one for time (t) — thus, for over a century, no experiment has been designed to sufficiently and accurately resolve each of these dimensions. Today, instruments comprising the revolutionary Fast Plasma Investigation onboard NASA's four spacecraft Magnetospheric Multiscale mission, flying over 40,000 miles away from Earth through regions where the magnetic fields of the Earth and Sun collide, equip space scientists with data collected at higher resolution than ever before achieved — high enough to at last resolve terms in the Vlasov equation for the first time in history, which we demonstrate here. Key Points: Bipolar and quadrupolar structures in the spatial gradient term of the electron Vlasov equation were measured for the first time with MMSElectron‐scale current layers exhibit alternating velocity space crescent structures in electron phase space density gradient distributionsEnergy conversion was observed in thin diamagnetic current layers in the magnetopause reconnection exhaust far from the diffusion region [ABSTRACT FROM AUTHOR]

While vorticity defined as the curl of the velocity has been broadly used in fluid and plasma physics, this quantity has been underutilized in space physics due to low time resolution observations. We report Magnetospheric Multiscale (MMS) observations of enhanced electron vorticity in the vicinity of the electron diffusion region of magnetic reconnection. On 11 July 2017 MMS traversed the magnetotail current sheet, observing tailward‐to‐earthward outflow reversal, current‐carrying electron jets in the direction along the electron meandering motion or out‐of‐plane direction, agyrotropic electron distribution functions, and dissipative signatures. At the edge of the electron jets, the electron vorticity increased with magnitudes greater than the electron gyrofrequency. The out‐of‐plane velocity shear along distance from the current sheet leads to the enhanced vorticity. This, in turn, contributes to the magnetic field perturbations observed by MMS. These observations indicate that electron vorticity can act as a proxy for delineating the electron diffusion region of magnetic reconnection. Plain Language Summary: Magnetic reconnection, causing explosive magnetic energy conversion into particle energy, is one of the most fundamental physical processes occurring both within the heliosphere and throughout the universe. The multiscale kinetic structures associated with reconnection have long been a focus in space plasma physics. We investigated how electron vorticity, a physical quantity widely used in fluid physics, but underutilized in the plasma, in particular, reconnection physics, enables us to delineate multiscale kinetic boundaries of reconnection sites using the unprecedented time resolution data from National Aeronautics and Space Administration's Magnetospheric Multiscale spacecraft. The magnitude of electron vorticity to be compared with the electron gyrofrequency provides a frame‐independent indicator of the electron diffusion region, therefore, greatly advancing our ability to delineate the multiscale reconnection boundaries. This study, directly relevant to plasma/reconnection physics, will improve our understanding of fundamental physics with far‐reaching implications in astrophysics. Key Points: We report MMS observation of enhanced electron vorticity in the reconnection siteThe magnitude of electron vorticity greater than the electron gyrofrequency indicates the electron diffusion region of magnetic reconnectionThe enhanced electron vorticity contributes to magnetic field perturbations observed by MMS [ABSTRACT FROM AUTHOR]

The unprecedented detail of measurements by the four Magnetospheric Multiscale (MMS) spacecraft enable deeper investigation of quasi‐perpendicular collisionless shocks. We compare shock normals, planarities, and Normal Incidence Frame cross‐shock potentials determined from electric field measurements and proxies, for a subcritical interplanetary shock and a supercritical bow shock. The subcritical shock's cross‐shock potential was 26±6 V. The shock scale was 33 km, too short to allow comparison with proxies from ion moments. Proxies from electron moments provided potential estimates of 40±5 V. Shock normals from magnetic field minimum variance analysis were nearly identical, indicating a planar front. The supercritical shock's cross‐shock potential was estimated to be from 290 to 440 V from the different spacecraft measurements, with shock scale 120 km. Reflected ions contaminated the ion‐based proxies upstream, whereas electron‐based proxies yielded reasonable estimates of 250±50 V. Shock normals from electric field maximum variance analysis differed, indicating a rippled front. Plain Language Summary: An important problem in shock physics is understanding how the incoming plasma flow is thermalized across the shock. The role of the cross‐shock electric field has not been well studied. We compare measurements and implicit estimates of cross‐shock potential for a quasi‐perpendicular weak (low Mach) shock and a quasi‐perpendicular strong (moderate/high Mach) shock using data from the four Magnetospheric Multiscale satellites. The weak shock had lower cross‐shock potential in the Normal Incidence Frame (about 30 V) than the strong shock (about 300 V). We also estimated the potential deduced from ion and electron data. Electron‐based estimates agreed reasonably well with the measurements, but ion‐based estimates encountered problems. The weak shock was too short compared to the ion data sampling period, while the strong shock reflected ions back into the upstream flow. Data from individual spacecraft indicated that the surface of the strong shock was not flat but rippled, one reason why its measured potential showed such a broad range. Key Points: We compared cross‐shock potential structure of two quasi‐perpendicular shocks (low/high Mach) in Magnetospheric Multiscale mission dataThe Normal Incidence Frame cross‐shock potential was 26 +/‐ 6 V for low‐Mach shock, 290‐440 V for high‐Mach shock, similar to electron proxiesAt the high‐Mach shock, ion proxies were spoiled by ions reflected off the rippled front [ABSTRACT FROM AUTHOR]

The most intense currents in the solar wind are carried by magnetic field discontinuities. The formation of such structures depends on whether they are rotational or tangential discontinuities. To distinguish between these two types, variations of plasma characteristics should be studied. We analyze data from a set of discontinuities observed by the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun and Magnetospheric Multiscale missions in the near‐Earth solar wind. We show that these discontinuities have properties characteristic of both tangential and rotational discontinuities: (1) Jumps in the tangential velocity component are well correlated with jumps in the Alfven speed, and (2) Electron density and temperature vary significantly across these discontinuities. Suprathermal electron pitch angle distributions change across discontinuities, revealing the importance of electron kinetics to discontinuity structure. Investigation of the discontinuity formation needs to go beyond magnetohydrodynamics theory and highly likely involves both ion and electron kinetics. Plain Language Summary: The most intense currents in the solar wind are carried by magnetic field discontinuities, coherent structures that contribute significantly to plasma heating and magnetic field fluctuations. Although investigation of discontinuities was started with the first spacecraft in situ measurements in the solar wind, we still do not know the primary mechanism of the discontinuity formation. Conclusions of the simplified fluid models of discontinuities often do not describe the observed discontinuity properties. In this study we investigate the nonfluid (kinetic) properties of these discontinuities. Such investigation becomes possible owing to unprecedented detailed plasma measurements provided by the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun and Magnetospheric Multiscale missions in the near‐Earth solar wind. Our findings show that observed discontinuity classification needs to go beyond fluid theory and highly likely involves both ion and electron kinetics. Key Points: Magnetic field discontinuities in solar wind are investigated using multispacecraft observationsObserved discontinuities have properties characteristic of both rotational and tangential discontinuitiesElectron pitch angle distributions vary sharply across the observed discontinuities [ABSTRACT FROM AUTHOR]

Abstract: We consider intense electrostatic solitary waves (ESW) observed in a supercritical quasi‐perpendicular Earth's bow shock crossing by the Magnetospheric Multiscale Mission. The ESW have spatial scales of a few tens of meters (a few Debye lengths) and propagate oblique to a local quasi‐static magnetic field with velocities from a few tens to a few hundred kilometers per second in the spacecraft frame. Because the ESW spatial scales are comparable to the separation between voltage‐sensitive probes, correction factors are used to compute the ESW electric fields. The ESW have electric fields with amplitudes exceeding 600 mV/m (oriented oblique to the local magnetic field) and negative electrostatic potentials with amplitudes of a few tenths of the electron temperature. The negative electrostatic potentials indicate that the ESW are not electron phase space holes, while interpretation in terms of ions phase space holes is also questionable. Whatever is their nature, we show that due to the oblique electric field orientation the ESW are capable of efficient pitch‐angle scattering and isotropization of thermal electrons. Due to the negative electrostatic potentials the ESW Fermi reflects a significant fraction of the thermal electrons streaming from upstream (downstream) back to upstream (downstream) region, thereby affecting the shock dynamics. The role of the ESW in electron heating is discussed. [ABSTRACT FROM AUTHOR]

Abstract: We report Magnetospheric Multiscale observations of electron pressure gradient electric fields near a magnetic reconnection diffusion region using a new technique for extracting 7.5 ms electron moments from the Fast Plasma Investigation. We find that the deviation of the perpendicular electron bulk velocity from E × B drift in the interval where the out‐of‐plane current density is increasing can be explained by the diamagnetic drift. In the interval where the out‐of‐plane current is transitioning to in‐plane current, the electron momentum equation is not satisfied at 7.5 ms resolution. [ABSTRACT FROM AUTHOR]

Electron pitch angle (Dαα) and momentum (Dpp) diffusion coefficients have been calculated due to resonant interactions with electrostatic electron cyclotron harmonic(ECH) and whistler mode choruswaves. Calculations have been performed at two spatial locations L = 4.6 and 6.8 for electron energies ≤10 keV. Landau (n = 0) resonance and cyclotron harmonicresonances n = ±1, ±2, ... ±5 have been included in the calculations. It is found that diffusion coefficient versus pitch angle (α) profiles show large dips and oscillations or banded structures. The structures are more pronounced for ECH and lower band chorus (LBC) and particularly at location 4.6. Calculations of diffusion coefficients have also been performed for individual resonances. It is noticed that the main contribution of ECHwaves in pitch angle diffusion coefficient is due to resonances n = +1 and n = +2. A major contribution to momentum diffusion coefficients appears from n = +2. However, the banded structures in Dαα and Dpp coefficients appear only in the profile of diffusion coefficients for n = +2. The contribution of other resonances to diffusion coefficients is found to be, in general, quite small or even negligible. For LBC and upper band choruswaves, the banded structures appear only in Landau resonance. The Dppdiffusion coefficient for ECHwaves is one to two orders smaller than Dαα coefficients. For choruswaves, Dpp coefficients are about an order of magnitude smaller than Dαα coefficients for the case n ≠ 0. In case of Landau resonance, the values of Dpp coefficient are generally larger than the values of Dαα coefficients particularly at lower energies. As an aid to the interpretation of results, we have also determined the resonant frequencies. For ECHwaves, resonant frequencies have been estimated for wave normal angle 89° and harmonicresonances n = +1, +2, and +3, whereas for whistler mode waves, the frequencies have been calculated for angle 10° and Landau resonance. Further, in ECHwaves, the banded structures appear for electron energies ≥1 keV, and for whistler mode choruswaves, structures appear for energies >2 keV at L = 4.6 and above 200 eV for L = 6.8. The results obtained in the present work will be helpful in the study of diffusion curves and will have important consequences for diffuse aurora and pancake distributions. [ABSTRACT FROM AUTHOR]

The Fast Plasma Investigation (FPI) was developed for flight on the Magnetospheric Multiscale (MMS) mission to measure the differential directional flux of magnetospheric electrons and ions with unprecedented time resolution to resolve kinetic-scale plasma dynamics. This increased resolution has been accomplished by placing four dual 180-degree top hat spectrometers for electrons and four dual 180-degree top hat spectrometers for ions around the periphery of each of four MMS spacecraft. Using electrostatic field-of-view deflection, the eight spectrometers for each species together provide 4pi-sr field-of-view with, at worst, 11.25-degree sample spacing. Energy/charge sampling is provided by swept electrostatic energy/charge selection over the range from 10 eV/q to 30000 eV/q. The eight dual spectrometers on each spacecraft are controlled and interrogated by a single block redundant Instrument Data Processing Unit, which in turn interfaces to the observatory's Instrument Suite Central Instrument Data Processor. This paper describes the design of FPI, its ground and in-flight calibration, its operational concept, and its data products. [ABSTRACT FROM AUTHOR]

The article discusses physical tests undertaken by DI-Aries, an energy-mass ion spectrometer used for space research to measure the energy distribution function of ion component of plasma which was developed by Phobes-Grunt space mission by the Russian Space Agency. Topics discussed include electro-optical plan of DI-Aries, DI-Aries being tested in a automatic vacuum chamber with ion source and satisfactory value of mass and image characteristics being observed.

One of the main goals of the Phobos-Grunt project is to analyze the surface composition of Phobos. Plasma methods of the studies make it possible to complete direct surface studies with measurements of the minor components of the solar wind, which are produced when a material sputtered from the surface of Phobos is ionized. The surface of Phobos is sputtered under the action of solar wind protons, energetic ions, hard solar radiation, and meteorites. In addition to the studies of Phobos, the experiment also includes the study of the interaction between the solar wind and Mars. An energy-mass spectrometer, which makes it possible to measure instantaneously complete unobscured distribution of the flux of different ions in the hemisphere, has been designed based on the new CAMERA analyzer of charged particles proposed previously (Vaisberg et al., 2001, 2005; Vaisberg, 2003). The instrument's electro-optics model and the results of the numerical and laboratory tests are described in this paper. Such an instrument can be used in magnetospheric studies and to study different objects of the Solar System. [ABSTRACT FROM AUTHOR]

A numerical model of an ion mass-spectrometer is developed based on the new type of charged-particle analyzer CAMERA suggested previously [1–3]. The spectrometer provides for complete instantaneous imaging of the flux distribution of various ions in a hemisphere. Such a type of the mass-spectrometer is chosen, which allows one to analyze a conelike beam of ions at the exit of the CAMERA. The mathematical model of the CAMERA with this time-of-flight mass-analyzer ensures sufficiently high mass resolution ( M/ΔM > 100) at conserved imaging capabilities of the CAMERA. Such an instrument can find a wide application both in magnetospheric studies and in studying various objects of the solar system. [ABSTRACT FROM AUTHOR]

Multi-spacecraft tracing of the high latitude magnetopause (MP) and boundary layers and Interball-1 statistics indicate that:

A new phenomenon was discovered on the basis of analysis of the Interball project data. A hot plasma flow is thermalized through the formation of “long-operating” vortex streets and local discontinuities and solitons in a distributed region over polar cusps. Plasma percolation through the structured boundary and secondary reconnection of fluctuating magnetic fields in a high-latitude turbulent boundary layer account for the main part of solar wind plasma inflow into the magnetospheric trap. Unlike local shocks, the ion thermalization is accompanied by the generation of coherent Alfvén waves on the scales ranging from ion gyroradius to the radius of curvature of the averaged magnetic field, as well as by the generation of diamagnetic bubbles with a demagnetized heated plasma inside. This “boiling” plasma has a frequency region where the spectrum is different from the Kolmogorov law (with slopes 1.2 and 2.4 instead of 5/3 or 3/2). The fluctuation self-organization in the boundary layer (synchronization of three-wave decays) was observed on certain frequency scales. © 2001 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Fully kinetic simulations of asymmetric magnetic reconnection reveal the presence of magnetic-field-aligned beams of electrons flowing toward the topological magnetic x line. Within the ~ 6de electron-diffusion region, the beams become oblique to the local magnetic field, providing a unique signature of the electron-diffusion region where the electron frozen-in law is broken. The numerical predictions are confirmed by in situ Magnetospheric Multiscale spacecraft observations during asymmetric reconnection at Earth's dayside magnetopause. [ABSTRACT FROM AUTHOR]

Supported by a kinetic simulation, we derive an exclusion energy parameter EX providing a lower kinetic energy bound for an electron to cross from one inflow region to the other during magnetic reconnection. As by a Maxwell demon, only high-energy electrons are permitted to cross the inner reconnection region, setting the electron distribution function observed along the low-density side separatrix during asymmetric reconnection. The analytic model accounts for the two distinct flavors of crescent-shaped electron distributions observed by spacecraft in a thin boundary layer along the low-density separatrix. [ABSTRACT FROM AUTHOR]

Collisionless shock nonstationarity arising from microscale physics influences shock structure and particle acceleration mechanisms. Nonstationarity has been difficult to quantify due to the small spatial and temporal scales. We use the closely spaced (subgyroscale), high-time-resolution measurements from one rapid crossing of Earth's quasiperpendicular bow shock by the Magnetospheric Multiscale (MMS) spacecraft to compare competing nonstationarity processes. Using MMS's high-cadence kinetic plasma measurements, we show that the shock exhibits nonstationarity in the form of ripples. [ABSTRACT FROM AUTHOR]