Pluto's Interaction With Energetic Heliospheric Ions

Pluto energies of a few kiloelectron volts and suprathermal ions with tens of kiloelectron volts and above. We measure this population using the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument on board the New Horizons spacecraft that flew by Pluto in 2015. Even though the measured ions have gyroradii larger than the size of Pluto and the cross section of its magnetosphere, we find that the boundary of the magnetosphere is depleting the energetic ion intensities by about an order of magnitude close to Pluto. The intensity is increasing exponentially with distance to Pluto and reaches nominal levels of the interplanetary medium at about 190R _P distance. Inside the wake of Pluto, we observe oscillations of the ion intensities with a periodicity of about 0.2 hr. We show that these can be quantitatively explained by the electric field of an ultralow-frequency wave and discuss possible physical drivers for such a field. We find no evidence for the presence of plutogenic ions in the considered energy range.

The Space Physics Environment Data Analysis System (SPEDAS)

With the advent of the Heliophysics/Geospace System Observatory (H/GSO), a complement of multi-spacecraft missions and ground-based observatories to study the space environment, data retrieval, analysis, and visualization of space physics data can be daunting. The Space Physics Environment Data Analysis System (SPEDAS), a grass-roots software development platform (www.spedas.org), is now officially supported by NASA Heliophysics as part of its data environment infrastructure. It serves more than a dozen space missions and ground observatories and can integrate the full complement of past and upcoming space physics missions with minimal resources, following clear, simple, and well-proven guidelines. Free, modular and configurable to the needs of individual missions, it works in both command-line (ideal for experienced users) and Graphical User Interface (GUI) mode (reducing the learning curve for first-time users). Both options have "crib-sheets," user-command sequences in ASCII format that can facilitate record-and-repeat actions, especially for complex operations and plotting. Crib-sheets enhance scientific interactions, as users can move rapidly and accurately from exchanges of technical information on data processing to efficient discussions regarding data interpretation and science. SPEDAS can readily query and ingest all International Solar Terrestrial Physics (ISTP)-compatible products from the Space Physics Data Facility (SPDF), enabling access to a vast collection of historic and current mission data. The planned incorporation of Heliophysics Application Programmer's Interface (HAPI) standards will facilitate data ingestion from distributed datasets that adhere to these standards. Although SPEDAS is currently Interactive Data Language (IDL)-based (and interfaces to Java-based tools such as Autoplot), efforts are under-way to expand it further to work with python (first as an interface tool and potentially even receiving an under-the-hood replacement). We review the SPEDAS development history, goals, and current implementation. We explain its "modes of use" with examples geared for users and outline its technical implementation and requirements with software developers in mind. We also describe SPEDAS personnel and software management, interfaces with other organizations, resources and support structure available to the community, and future development plans.

ELECTRONIC SUPPLEMENTARY MATERIAL

The online version of this article (10.1007/s11214-018-0576-4) contains supplementary material, which is available to authorized users.

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 mechanism^1,2, 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 edges^5,10, and potentially contribute to particle acceleration^11-13, 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 acceleration^14,15. 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.

A mass analysis technique using coincidence measurements from the Interstellar Boundary Explorer-Hi (approximately 0.3- approximately 6 keV) detector

NASA's Interstellar Boundary Explorer (IBEX) mission, scheduled to launch in October 2008, will make the first observations of charge exchange energetic neutral atoms (ENAs) produced near the edge of the heliosphere. IBEX will measure these ENAs with two ultra-high sensitivity, single-pixel ENA sensors in the energy range of approximately 0.01- approximately 2 keV (IBEX-Lo) and approximately 0.3- approximately 6 keV (IBEX-Hi), respectively. The primary purpose of IBEX is to measure hydrogen ENAs from the outer heliosphere, but it will also be sensitive to heavier species of ENAs produced anywhere throughout the solar system. For this study, we measured the coincidence response of the IBEX-Hi detector section to H, He, N, and O ions. Based on these results, we have developed an innovative technique in estimating the hydrogen to heavy ion ratio in the signal. This new technique can be applied more widely than the IBEX-Hi detector section, and the basic principle may be useful for other, future space and ground-based measurements.

The Process of Tholin Formation in Titan's Upper Atmosphere

Titan's lower atmosphere has long been known to harbor organic aerosols (tholins) presumed to have been formed from simple molecules, such as methane and nitrogen (CH4 and N2). Up to now, it has been assumed that tholins were formed at altitudes of several hundred kilometers by processes as yet unobserved. Using measurements from a combination of mass/charge and energy/charge spectrometers on the Cassini spacecraft, we have obtained evidence for tholin formation at high altitudes (approximately 1000 kilometers) in Titan's atmosphere. The observed chemical mix strongly implies a series of chemical reactions and physical processes that lead from simple molecules (CH4 and N2) to larger, more complex molecules (80 to 350 daltons) to negatively charged massive molecules (approximately 8000 daltons), which we identify as tholins. That the process involves massive negatively charged molecules and aerosols is completely unexpected.

C-band polymorphism: comparison between trisomy 21 cases and mentally retarded controls

C-banding was done prospectively on 50 Down syndrome (trisomy 21) cases and 50 mentally retarded controls. Heterochromatin was quantitated by measuring the lengths of heterochromatin blocks and comparing these segments to the length of the short arm of chromosome 16 for 1, 9 and 16 heterochromatin, and to the total length of the Y chromosome for the Y heterochromatin in the distal long arm. For the first 30 individuals in each group, there was no difference in the mean lengths of C-band blocks of the 1, 9, 16 and Y chromosomes. For the total sample, there also was no difference between the trisomy 21 cases and controls in the number or size of pericentric inversions involving the heterochromatin blocks of chromosomes 1 and 9. Assuming random segregation of the parental C-band polymorphisms, this study gives no evidence for an association between such polymorphisms of the 1, 9, 16 and Y chromosomes and nondisjunction of chromosome 21.

Prominent acrocentric chromosome satellites in child patients with mental retardation or psychiatric disorders; no IQ-satellite size correlation

Child patients with mental retardation or psychiatric disorders were selected for the presence of prominent acrocentric chromosome satellites and highest or lowest IQ scores. No correlation was found between IQ scores, of which eleven were below IQ 54 and 16 above IQ 68, and the length of acrocentric short arm, satellite, stalk, or short arm material below the stalk. Conventional staining, quinacrine fluorescence, C banding and ammoniacal silver staining revealed the apparent same acrocentric short arm variation between patient and one parent in eight families studied. These findings suggest that the satellite variants were truly normal variants and not etiologically related to the developmental disorders seen in the patients.

Estimation of the variance components for dermal ridge count

Refinements of the scoring algorithm to estimate variance components from pedigree data are developed. Subsequent to these modifications, heritability estimates were readily obtained from data for over 50 traits, including total finger ridge count reported here. A significant contribution to the total variance of ridge count could be attributed to the effects of dominance, a finding not previously reported for this dermatoglyphic trait.

Extensions to pedigree analysis. III. Variance components by the scoring method

The classic variance components for simple polygenic traits - additive, dominance, and environmental variance - have traditionally been estimated from sample covariances between first-degree relatives. If data is gathered on pedigrees, this statistical procedure wastes information. Recently Elston & Stewart suggested an alternative likelihood procedure that uses all the information in a set of pedigrees. A refinement of their method based on the scoring technique gives rapidly converging maximum likelihood estimates of the variance components and of the male and female means. Tests of statistical hypotheses about the various parameters can then be made by the likelihood ratio method. Furthermore, using classical regression analysis, the estimated parameter values allow prediction of unknown trait values from known trait values within a pedigree. These methods should apply to traits like total finger ridge count and to quantitative measurements associated with disease traits. Since the model postulates independent environmental effects and no assortative mating, its utility in human behaviour genetics seems limited.

Estimation of polygenic recurrence risk for cleft lip and palate

Data on cleft lip with or without cleft palate are utilized to evaluate a new method for estimating recurrence risk under the polygenic threshold model. The influence of critical factors on the accuracy of the estimated risks are evaluated. The model is relatively sensitive to the estimate of heritability employed and relatively robust to the population prevalence estimate and to family size. The calculated risks for cleft lip with or without cleft palate are contrasted with the empiric figures from studies on Caucasians and Japanese populations.