Global observations of He+ ions from the Imager for Magnetopause-to-Aurora Global Exploration mission Extreme Ultraviolet Imager are used to examine the dynamics of plasmasphere content using integrated mass through times of erosion and refilling for 1.5 <= L <= 5.5. Perhaps the most basic and important attributes of the plasmasphere are its mass and spatial distribution. However, our understanding is often constrained by the method of measurement. Storm-time loss of plasmasphere content is a kind of exhalation where plasma is lost. Refilling or inhalation into the body of the plasmasphere occurs during the following calm. Using a follow-the-mass approach, storm-time plasmasphere loss for 1.5 <= L<5.5 is found to range from 32% to 62% during three events. Plasma lost inside the average eroded plasmapause boundary ranges from 22% to 42% and outside from 35% to 72%. Following the start of refilling, the innermost L-shells show the lowest observed refilling rates. Mass refilling rates at higher L-shells rise to a maximum observed similar to 6 Mt/day near L = 4.5 that is less at higher L-shells (Mt/d = 1,000 kg/day). More variability and higher refilling rates are found during lower solar activity. The mass content of the plasmasphere between L = 1.5 and 3.0 was also followed for 54 days when it exhibited eight "breathes." Using this analogy, only the first inhale/exhale is "deep." The remaining carry forward the consequences of past and continued activity that prevents full recovery. There appears to be a month-long declining trend in the mass of the inner plasmasphere during the last two thirds of this time.

As demonstrated by IMAGE-EUV observations, plasmaspheric drainage plumes are a common feature emanating from the plasmasphere during periods of enhanced convection. Concurrent IMAGE-EUV and LANL-MPA observations reveal that plasmaspheric plumes are not a uniform density structure that extends out to geosynchronous orbit and beyond. Instead, in- situ observations reveal a large spatial-scale structure populated by small-scale density structures suggestive of the presence of a turbulent process. Here, we investigate the occurrence and n ature of plasmaspheric drainage plumes as observed by concurrent EUV-MPA observations, as well as explore the possibility that the in–situ observed small-scale density structures are the signature of an instability produced by the sheared velocity found within the plasmaspheric layers separating the corotation of the main plasmasphere from the convection- driven flow generating the plume. Particle-in-cell simulations indicate that the generation of shear-flow driven instabilities is possible under plasmaspheric plasma conditions. The initial results of these simulations indicate that the plasmaspheric instabilities generated are electrostatic in nature, consist with in–situ plume observations.

The four Magnetospheric Multiscale (MMS) spacecraft observed energetic ( E>50 keV) ion bursts exhibiting an inverse dispersion in the magnetosheath on 28 December 2015. We consider the possibility that these ions originate from the magnetosphere. The ion composition ratios, flux levels, and the spectral slopes of the energetic ion energy spectra observed in the foreshock and in the magnetosheath resemble those in the outer magnetosphere but differ significantly from those seen further upstream from the bow shock at ACE. The particle gyrocenters lie earthward from the spacecraft, indicating that the maximum ion fluxes come from close to the magnetosphere. We provide important evidence that argues against an explanation of the particle source in terms of hot flow anomaly acceleration. A three‐dimensional global hybrid simulation shows that escaping magnetospheric ions can be scattered and transported across the magnetosheath. Ground magnetometer observations suggest that a solar wind pressure increase accelerates escaping magnetospheric ions via betatron acceleration, resulting in an inverse energy dispersion in the magnetosheath. However, there are no pressure changes detected on the MMS and ACE spacecraft and the ground magnetic field strength does not appear to be large enough to be consistent with the large magnetospheric compression needed to account for a betatron acceleration. Therefore, we suggest that the inverse energy dispersion event can be explained by a magnetic field rotation that connects MMS to the subsolar magnetosphere, enabling high‐energy particles from deep within the inner magnetosphere gain access to the magnetopause and magnetosheath.

The solar wind electron velocity distribution function (eVDF) exhibits a variety of non-thermal features that deviate from thermal equilibrium. These deviations from equilibrium provide a local source for electromagnetic fluctuation emissions, including the commonly observed electron whistler-cyclotron and firehose instabilities. We present a systematic analysis of Wind-SWE-VEIS observations of solar wind electron plasma and associated Wind-MFI observed magnetic fluctuations. For the first time using the full solar wind electron distribution and its moments, without separation of the various electron components, we show clear evidence that the temperature anisotropy threshold of the parallel electron cyclotron anisotropic instability bounds solar wind electrons during slow solar wind periods. We also demonstrate that during periods of slow solar wind, collisions-while infrequent -are the dominant mechanism by which solar wind electrons are constrained, leading to isotropization. During fast solar wind periods, magnetic fluctuations and solar wind anisotropies are enhanced above the parallel whistler anisotropic threshold boundary and collisional effects are significantly reduced. Preliminary calculations further show that the oblique electron whistler mirror anisotropic instability bounds both the slow and fast solar wind. Regardless of speed, the solar wind electron thermal anisotropy appears globally bounded by the parallel electron firehose instability for anisotropiesT(e)perpendicular to/T-e parallel to < 1. Our results indicate that collisions, while infrequent, play a necessary role in regulating the solar wind eVDFs. In striking contrast to solar wind ions, solar wind electron plasma, when considered globally as a single eVDF, is only marginally stable with respect to parallel propagating instabilities.

We apply a scalar measure of nongyrotropy to the electron pressure tensor in a 2D particle-in-cell simulation of guide field reconnection and assess the corresponding electron distributions and the forces that account for the nongyrotropy. The scalar measure reveals that the nongyrotropy lies in bands that straddle the electron diffusion region and the separatrices, in the same regions where there are parallel electric fields. Analysis of electron distributions and fields shows that the nongyrotropy along the inflow and outflow separatrices emerges as a result of multiple populations of electrons influenced differently by large and small-scale parallel electric fields and by gradients in the electric field. The relevant parallel electric fields include large-scale potential ramps emanating from the x-line and sub-ion inertial scale bipolar electron holes. Gradients in the perpendicular electric field modify electrons differently depending on their phase, thus producing nongyrotropy. Magnetic flux violation occurs along portions of the separatrices that coincide with the parallel electric fields. An inductive electric field in the electron E × B drift frame thus develops, which has the effect of enhancing nongyrotropies already produced by other mechanisms and under certain conditions producing their own nongyrotropy. Particle tracing of electrons from nongyrotropic populations along the inflows and outflows shows that the striated structure of nongyrotropy corresponds to electrons arriving from different source regions. We also show that the relevant parallel electric fields receive important contributions not only from the nongyrotropic portion of the electron pressure tensor but from electron spatial and temporal inertial terms as well.

Whistlers observed outside the plasmasphere by Cluster have been correlated with the global plasmasphere using Imager for Magnetopause‐to‐Aurora Global Exploration‐Extreme Ultraviolet Imager (IMAGE‐EUV) observations. Of the 12 Cluster‐observed whistler events reported, EUV is able to provide global imaging of the plasmasphere for every event and demonstrates a direct correlation between the detection of lightning‐generated whistlers beyond the plasmapause and the presence of a global perturbation of the local plasmapause. Of these 12 correlated events, seven of the Cluster‐observed whistlers (or 58%) are associated with the Cluster spacecraft lying radially outward from a plasmaspheric notch. Two of the Cluster‐observed whistlers (17%) are associated with the low‐density region between the late afternoon plasmapause and the western wall of a plasmaspheric drainage plume. The final three Cluster‐observed whistler events (25%) are associated with a nonradial, nonazimuthal depletion in plasmaspheric He+ emission that are termed “notch‐like” crenulations. In one of these cases, the notch‐like crenulations appear to be manifestations entrained within the plasmasphere boundary layer of a standing wave on the surface of the plasmasphere. The correlated Cluster/IMAGE‐EUV observations suggest that the depleted flux tubes that connect the ionosphere to the low‐density regions of plasmaspheric trough and inner magnetosphere facilitate the escape of whistler waves from the plasmasphere.

Plasma measurements in space are becoming increasingly faster, higher resolution, and distributed over multiple instruments. As raw data generation rates can exceed available data transfer bandwidth, data compression is becoming a critical design component. Data compression has been a staple of imaging instruments for years, but only recently have plasma measurement designers become interested in high performance data compression. Missions will often use a simple lossless compression technique yielding compression ratios of approximately 2:1, however future missions may require compression ratios upwards of 10:1. This study aims to explore how a Discrete Wavelet Transform combined with a Bit Plane Encoder (DWT/BPE), implemented via a CCSDS standard, can be used effectively to compress count information common to plasma measurements to high compression ratios while maintaining little or no compression error. The compression ASIC used for the Fast Plasma Investigation (FPI) on board the Magnetospheric Multiscale mission (MMS) is used for this study. Plasma count data from multiple sources is examined: resampled data from previous missions, randomly generated data from distribution functions, and simulations of expected regimes. These are run through the compression routines with various parameters to yield the greatest possible compression ratio while maintaining little or no error, the latter indicates that fully lossless compression is obtained. Finally, recommendations are made for future missions as to what can be achieved when compressing plasma count data and how best to do so.

Direct measurement of low <1eV electron temperature is difficult to make in the Earth's inner magnetosphere for electron densities (N-e)<3x10(2) cm(-3). We compute these quantities by solving current balance equations in low-density regions. Concurrent measurements from the Polar spacecraft of the relative potential (V-S-V-P), between the spacecraft body and the electric field probe, and the electron density (N-e), derived from upper hybrid frequency (f(UHR)), were used in the current balance equations to solve for the electron temperature (T-e), V-s, and V-p. Where V-P is the probe potential and V-S is the spacecraft potential relative to the nearby plasma. The assumption that the bulk plasma electrons are Maxwellian is used in the computations. Our data set covered 1.5years of measurements when f(UHR) was detectable (L<10). The following averaged T-e versus L relation for 3<L<5 was obtained: T-e=0.58+0.49(L-3)eV. This expression is in reasonable agreement with extrapolations of ionospheric T-e measurements by Akebono at lower altitudes. However, the solution is sensitive to the photoemission coefficients, substituting those of Scudder et al. (2000) with those of Escoubet et al. (1997), the T-e curve shifted upward by similar to 1eV. Also, the solution is sensitive to measurement error of V-S-V-P, applying a voltage shift of 0.1 and 0.2V to V-S-V-P, the relative median error for our data set was computed to be 0.27 and 1.04, respectively. We believe that our T-e values computed outside the plasmasphere are unrealistically low. We conclude that this method shows promise inside the plasmasphere but should be used with caution. We also quantified the N-e versus V-S-V-P relationship. The running median N-e versus V-S-V-P curve shows no significant variation over the 1.5year period of the data set, suggesting that the photoemission coefficients did not change significantly over this time span. The Scudder et al. (2000) N-e model, based on only one Polar orbit, is in reasonable agreement (within a factor of 2) with our results.

The electron‐velocity‐distribution function was determined to be highly non‐Maxwellian and more appropriate to a kappa distribution, with κ ≈ 2.0, near magnetic midnight in the low‐latitude magnetosphere just outside a stable plasmasphere during extremely quiet geomagnetic conditions. The kappa results were based on sounder‐stimulated Qn plasma resonances using the Radio Plasma Imager (RPI) on the IMAGE satellite; the state of the plasmasphere was determined from IMAGE/EUV observations. The Qn resonances correspond to the maximum frequencies of Bernstein‐mode waves that are observed between the harmonics of the electron cyclotron frequency in the frequency domain above the upper‐hybrid frequency. Here we present the results of a parametric investigation that included suprathermal electrons in the electron‐velocity‐distribution function used in the plasma‐wave dispersion equation to calculate the Qn frequencies for a range of kappa and f pe / f ce values for Qn resonances from Q1 to Q9. The Qn frequencies were also calculated using a Maxwellian distribution, and they were found to be greater than those calculated using a kappa distribution with the frequency differences increasing with increasing n for a fixed κ and with decreasing κ for a fixed n. The calculated f Qn values have been incorporated into the RPI BinBrowser software providing a powerful tool for rapidly obtaining information on the nature of the magnetospheric electron‐velocity‐distribution function and the electron number density N e . This capability enabled accurate (within a few percent) in situ N e determinations to be made along the outbound orbital track as IMAGE moved away from the plasmapause. The extremely quiet geomagnetic conditions allowed IMAGE/EUV‐extracted counts to be compared with the RPI‐determined orbital‐track N e profile. The comparisons revealed remarkably similar N e structures.

We investigate the distribution of parallel electric fields and their relationship to the location and rate of magnetic reconnection in a large particle-in-cell simulation of 3D turbulent magnetic reconnection with open boundary conditions. The simulation's guide field geometry inhibits the formation of simple topological features such as null points. Therefore, we derive the location of potential changes in magnetic connectivity by finding the field lines that experience a large relative change between their endpoints, i.e., the quasi-separatrix layer. We find a good correspondence between the locus of changes in magnetic connectivity or the quasi-separatrix layer and the map of large gradients in the integrated parallel electric field (or quasi-potential). Furthermore, we investigate the distribution of the parallel electric field along the reconnecting field lines. We find the reconnection rate is controlled by only the low-amplitude, zeroth and first-order trends in the parallel electric field while the contribution from fluctuations of the parallel electric field, such as electron holes, is negligible. The results impact the determination of reconnection sites and reconnection rates in models and in situ spacecraft observations of 3D turbulent reconnection. It is difficult through direct observation to isolate the loci of the reconnection parallel electric field amidst the large amplitude fluctuations. However, we demonstrate that a positive slope of the running sum of the parallel electric field along the field line as a function of field line length indicates where reconnection is occurring along the field line. (C) 2013 AIP Publishing LLC.

The Poincaré index indicates that the Cluster spacecraft tetrahedron entraps a number of 3‐D magnetic nulls during an encounter with the turbulent magnetosheath. Previous researchers have found evidence for reconnection at one of the many filamentary current layers observed by Cluster in this region. We find that many of the entrained nulls are also associated with strong currents. We dissect the current structure of a pair of spiral nulls that may be topologically connected. At both nulls, we find a strong current along the spine, accompanied by a somewhat more modest current perpendicular to the spine that tilts the fan toward the axis of the spine. The current along the fan is comparable to the that along the spine. At least one of the nulls manifests a rotational flow pattern in the fan plane that is consistent with torsional spine reconnection as predicted by theory. These results emphasize the importance of examining the magnetic topology in interpreting the nature of currents and reconnection in 3‐D turbulence.

This chapter contains sections titled: Introduction Instrument Description Laboratory Testing Flight Results Conclusions

We report our findings comparing the geometric factor (GF) as determined from simulations and laboratory measurements of the new Dual Electron Spectrometer (DES) being developed at NASA Goddard Space Flight Center as part of the Fast Plasma Investigation on NASA's Magnetospheric Multiscale mission. Particle simulations are increasingly playing an essential role in the design and calibration of electrostatic analyzers, facilitating the identification and mitigation of the many sources of systematic error present in laboratory calibration. While equations for laboratory measurement of the GF have been described in the literature, these are not directly applicable to simulation since the two are carried out under substantially different assumptions and conditions, making direct comparison very challenging. Starting from first principles, we derive generalized expressions for the determination of the GF in simulation and laboratory, and discuss how we have estimated errors in both cases. Finally, we apply these equations to the new DES instrument and show that the results agree within errors. Thus we show that the techniques presented here will produce consistent results between laboratory and simulation, and present the first description of the performance of the new DES instrument in the literature.

The Magnetospheric Multiscale (MMS) mission will study small-scale reconnection structures and their rapid motions from closely spaced platforms using instruments capable of high angular, energy, and time resolution measurements. To meet these requirements, the Fast Plasma Instrument (FPI) consists of eight (8) identical half top-hat electron sensors and eight (8) identical ion sensors and an Instrument Data Processing Unit (IDPU). The sensors (electron or ion) are grouped into pairs whose 6 degree x 180 degree fields-of-view (FOV) are set 90 degrees apart. Each sensor is equipped with electrostatic aperture steering to allow the sensor to scan a 45 degree x 180 degree fan about the its nominal viewing (0 deflection) direction. Each pair of sensors, known as the Dual Electron Spectrometer (DES) and the Dual Ion Spectrometer (DIS), occupies a quadrant on the MMS spacecraft and the combination of the eight electron/ion sensors, employing aperture steering, image the full-sky every 30-ms (electrons) and 150-ms (ions), respectively. To probe the diffusion regions of reconnection, the highest temporal/spatial resolution mode of FPI results in the DES complement of a given spacecraft generating 6.5-Mb (raised dot) per second of electron data while the DIS generates 1.1-Mb (raised dot) per second of ion data yielding an FPI total data rate of 6.6-Mb (raised dot) per second. The FPI electron/ion data is collected by the IDPU then transmitted to the Central Data Instrument Processor (CIDP) on the spacecraft for science interest ranking. Only data sequences that contain the greatest amount of temporal/spatial structure will be intelligently down-linked by the spacecraft. This requires a data ranking process known as the burst trigger system. The burst trigger system uses pseudo physical quantities to approximate the local plasma environments. As each pseudo quantity will have a different value, a set of two scaling factors is employed for each pseudo term. These pseudo quantities are then combined at the instrument, spacecraft, and observatory level leading to a final ranking of data based on expected scientific interest. Here, we present simulations of the fixed point burst trigger system for the FPI. A variety of data sets based on previous mission data as well as analytical formulations are tested. Comparisons of floating point calculations versus the fixed point hardware simulation are shown. Analysis of the potential sources of error from overflows, quantization, etc. are examined and mitigation methods are presented. Finally a series of calibration curves are presented, showing the expected error in pseudo quantities based solely on the scale parameters chosen and the expected data range. We conclude with a presentation of the current base-lined FPI burst trigger approach.

Magnetic turbulence and secondary island formation have reemerged as possible explanations for fast reconnection. Recent three-dimensional simulations reveal the formation of secondary islands that serve to shorten the current sheet and increase the accelerating electric field, while both simulations and observations witness electron holes whose collapse energizes electrons. However, few data studies have explicitly investigated the effect of turbulence and islands on the reconnection rate. We present a more comprehensive analysis of the effect of turbulence and islands on reconnection rates observed in space. Our approach takes advantage of multiple spacecraft to find the location of the spacecraft relative to the inflow and the outflow, to estimate the reconnection electric field, to indicate the presence and size of islands, and to determine wave vectors indicating turbulence. A superposed epoch analysis provides independent estimates of spatial scales and a reconnection electric field. We apply k-filtering and a new method adopted from seismological analyses to identify the wavevectors. From several case studies of reconnection events, we obtain preliminary estimates of the spectral scaling law, identify wave modes, and present a method for finding the reconnection electric field associated with the wave modes.