The Magnetic Electron Ion Spectrometer: A Review of On-Orbit Sensor Performance, Data, Operations, and Science.

Measurements from NASA's Van Allen Probes have transformed our understanding of the dynamics of Earth's geomagnetically-trapped, charged particle radiation. The Van Allen Probes were equipped with the Magnetic Electron Ion Spectrometers (MagEIS) that measured energetic and relativistic electrons, along with energetic ions, in the radiation belts. Accurate and routine measurement of these particles was of fundamental importance towards achieving the scientific goals of the mission. We provide a comprehensive review of the MagEIS suite's on-orbit performance, operation, and data products, along with a summary of scientific results. The purpose of this review is to serve as a complement to the MagEIS instrument paper, which was largely completed before flight and thus focused on pre-flight design and performance characteristics. As is the case with all space-borne instrumentation, the anticipated sensor performance was found to be different once on orbit. Our intention is to provide sufficient detail on the MagEIS instruments so that future generations of researchers can understand the subtleties of the sensors, profit from these unique measurements, and continue to unlock the mysteries of the near-Earth space radiation environment. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11214-021-00855-2.

Daytime Dynamo Electrodynamics With Spiral Currents Driven by Strong Winds Revealed by Vapor Trails and Sounding Rocket Probes.

We investigate the forces and atmosphere-ionosphere coupling that create atmospheric dynamo currents using two rockets launched nearly simultaneously on 4 July 2013 from Wallops Island (USA), during daytime Sq conditions with ΔH of -30 nT. One rocket released a vapor trail observed from an airplane which showed peak velocities of >160 m/s near 108 km and turbulence coincident with strong unstable shear. Electric and magnetic fields and plasma density were measured on a second rocket. The current density peaked near 110 km exhibiting a spiral pattern with altitude that mirrored that of the winds, suggesting the dynamo is driven by tidal forcing. Such stratified currents are obscured in integrated ground measurements. Large electric fields produced a current opposite to that driven by the wind, believed created to minimize the current divergence. Using the observations, we solve the dynamo equation versus altitude, providing a new perspective on the complex nature of the atmospheric dynamo.

A Revised Look at Relativistic Electrons in the Earth's Inner Radiation Zone and Slot Region.

We describe a new, more accurate procedure for estimating and removing inner zone background contamination from Van Allen Probes Magnetic Electron Ion Spectrometer (MagEIS) radiation belt measurements. This new procedure is based on the underlying assumption that the primary source of background contamination in the electron measurements at L shells less than three, energetic inner belt protons, is relatively stable. Since a magnetic spectrometer can readily distinguish between foreground electrons and background signals, we are able to exploit the proton stability to construct a model of the background contamination in each MagEIS detector by only considering times when the measurements are known to be background dominated. We demonstrate, for relativistic electron measurements in the inner zone, that the new technique is a significant improvement upon the routine background corrections that are used in the standard MagEIS data processing, which can "overcorrect" and therefore remove real (but small) electron fluxes. As an example, we show that the previously reported 1-MeV injection into the inner zone that occurred in June of 2015 was distributed more broadly in L and persisted in the inner zone longer than suggested by previous estimates. Such differences can have important implications for both scientific studies and spacecraft engineering applications that make use of MagEIS electron data in the inner zone at relativistic energies. We compare these new results with prior work and present more recent observations that also show a 1-MeV electron injection into the inner zone following the September 2017 interplanetary shock passage.

Autogenous and efficient acceleration of energetic ions upstream of Earth's bow shock.

Earth and its magnetosphere are immersed in the supersonic flow of the solar-wind plasma that fills interplanetary space. As the solar wind slows and deflects to flow around Earth, or any other obstacle, a 'bow shock' forms within the flow. Under almost all solar-wind conditions, planetary bow shocks such as Earth's are collisionless, supercritical shocks, meaning that they reflect and accelerate a fraction of the incident solar-wind ions as an energy dissipation mechanism1,2, which results in the formation of a region called the ion foreshock3. In the foreshock, large-scale, transient phenomena can develop, such as 'hot flow anomalies'4-9, which are concentrations of shock-reflected, suprathermal ions that are channelled and accumulated along certain structures in the upstream magnetic field. Hot flow anomalies evolve explosively, often resulting in the formation of new shocks along their upstream edges5,10, and potentially contribute to particle acceleration11-13, but there have hitherto been no observations to constrain this acceleration or to confirm the underlying mechanism. Here we report observations of a hot flow anomaly accelerating solar-wind ions from roughly 1-10 kiloelectronvolts up to almost 1,000 kiloelectronvolts. The acceleration mechanism depends on the mass and charge state of the ions and is consistent with first-order Fermi acceleration14,15. The acceleration that we observe results from only the interaction of Earth's bow shock with the solar wind, but produces a much, much larger number of energetic particles compared to what would typically be produced in the foreshock from acceleration at the bow shock. Such autogenous and efficient acceleration at quasi-parallel bow shocks (the normal direction of which are within about 45 degrees of the interplanetary magnetic field direction) provides a potential solution to Fermi's 'injection problem', which requires an as-yet-unexplained seed population of energetic particles, and implies that foreshock transients may be important in the generation of cosmic rays at astrophysical shocks throughout the cosmos.

Electron-scale measurements of magnetic reconnection in space.

Magnetic reconnection is a fundamental physical process in plasmas whereby stored magnetic energy is converted into heat and kinetic energy of charged particles. Reconnection occurs in many astrophysical plasma environments and in laboratory plasmas. Using measurements with very high time resolution, NASA's Magnetospheric Multiscale (MMS) mission has found direct evidence for electron demagnetization and acceleration at sites along the sunward boundary of Earth's magnetosphere where the interplanetary magnetic field reconnects with the terrestrial magnetic field. We have (i) observed the conversion of magnetic energy to particle energy; (ii) measured the electric field and current, which together cause the dissipation of magnetic energy; and (iii) identified the electron population that carries the current as a result of demagnetization and acceleration within the reconnection diffusion/dissipation region.

Prenatal diagnosis of autosomal recessive polycystic kidney disease: variable outcome within one family.

Autosomal recessive polycystic kidney disease is frequently diagnosed in utero by obstetric ultrasonography. We report a case in which there were varying outcomes of this disorder in three affected fetuses in a family. Recognition of variable expression within one family is important when parents are considering termination of a pregnancy with an affected fetus.

Familial neonatal hemochromatosis with survival.

We report two sisters with neonatal hemochromatosis (NHC), including the first documented survivor. Characterized by excessive parenchymal iron in liver, pancreas, heart, and other organs, but little iron in the spleen, bone marrow, or other sites of the reticuloendothelial system, NHC is rarely reported and has been uniformly fatal. The first infant (case 1) presented with neonatal hypoglycemia, coagulopathy, and mild hyperbilirubinemia; she rapidly deteriorated and died of multisystem failure. Autopsy showed cirrhosis. Her sister (case 2) presented similarly; liver biopsy showed giant cell hepatitis, which is consistent with idiopathic neonatal hepatitis (INHP). However, iron staining revealed that case 1 had extensive iron deposits in the liver, pancreas, heart, thymus, and bone, but none in bone marrow or spleen. Case 2 had grade 4 liver iron staining, normal bone marrow iron, elevated serum ferritin and transferrin saturation, and HLA-A3 haplotype. At 16 months of age, the growth, development, and serum measures of iron status in case 2 were normal; liver biopsy showed fibrosis, negative iron staining, and normal tissue iron concentration. NHC is compatible with survival, has clinicopathologic features that overlap with INHP, and may frequently be misdiagnosed as INHP. A prospective study is needed to determine the incidence and natural history of NHC--a disorder that may be more common than is currently recognized.

Trisomy 18 with ectopia cordis, omphalocele, and ventricular septal defect: case report.

A case of thoracoabdominal ectopia cordis was diagnosed by ultrasonography at 21 weeks' gestation. Chromosomal analysis showed full trisomy 18. This case supports the associational of thoracoabdominal ectopia cordis (Cantrell's pentad) with chromosomal errors, specifically trisomy 18.

Infantile lymphoblastic leukemia with t(4;11) and septate uterus, double cervix, and double vagina: case report and review of the literature.

Translocation between chromosomes 4 and 11 has been associated with an aggressive subtype of acute lymphoblastic leukemia. To date, 32 cases have been reported, 12 of which have been in infants. We report the 13th infantile case and the first associated with a somatic abnormality (septate uterus with double cervix and double vagina).